China's first carbon-14 chronology laboratory

    Zhang Xuelian (hereinafter referred to as Zhang): at the end of the 1940s and the early the 1950s, scientists in the United States established the carbon-14 dating method. This method was applied in the West soon after it was discovered Our famous archaeologist Mr. Xiading introduced the method that carbon-14 chronology turned relative age into an absolute age, which impacted archaeology greatly, known as a revolution in the archaeological world. On this international stage, the Chinese chronology of prehistoric archaeology wanted to have some room, it was necessary to get the support of carbon-14 chronology, which means Chinese people could meet the challenges in the science field. As the first person to introduce this revolution into China, how were you transferred from the institute of atomic energy research to the archaeological institute and from nuclear energy research to the research of carbon-14 chronology to meet this challenge?

    Qiu Shihua (hereinafter referred to as Qiu): in 1955, my wife, Cai Lianzhen and I both graduated from the physics department of Fudan University (the former Modern Physics Institute). This is an institute which was committed to the basic research of atomic energy, and Qian Sanqiang served as the director. There were some scientists who came from abroad serving as the directors of every research area and the directors of projects, so in this way they lead the young scholars to do study work. Served as the director of the fifth research room (radioactive chemistry), Yang Zongcheng came from the French Curie lab, who was a respected and famous scientist. After we joined in, we were assigned to the second research institute, and we worked while training. In 1956, our country called for the youth to devote themselves to science, so it was natural that we became absorbed with our work and study. However, it didn’t last long, and, at the end of spring and early summer of 1957, my wife and I were both classified as “the Rightists". Our teachers were worried about us but helpless. Soon after, we were sent to the countryside to be reformed, and our fates changed from then. It was unexpected that in this critical moment, out of the love for the young, and the zeal and loyalty of science, Mr.Yang recommended us to Mr. Xianai who was the deputy director of the archaeological research institute. At that moment, they were friends and neighbors. Originally, Mr. Xia had been calling for the establishment of a carbon-14 chronology laboratory for a long time, but there were no suitable people and the timing wasn’t right. At this time, Mr. Xia took this opportunity to have us transferred from Qian Sanqiang and he said: “you work is of a strong confidential nature, we can use it”. Then, we were transferred to the archaeological institute.

    In early 1959, when we came to the archaeological institute, Mr. Xia showed us a book Radiocarbon Dating written by W.F.Libby and published in 1955. He asked us to be responsible for the establishment of a carbon-14 chronology laboratory. At that time, there was no domestic laboratory for reference, no factories that manufactured these kinds of instruments and also the wireless parts were also insufficient. The archaeological institute asked us to warm ourselves by burning coal and not worry about conditions in the lab. What should we do when faced with this situation? We were college students cultivated by our country after the founding of the new China. Although we were classified as “the Rightists", we should try our best to repay our country and people. Since the leader of archaeology gave this tough task to us, we should be grateful and try our best to overcome the challenges that we met. We would use our performance to let our Party and people know that we serving our country sincerely. It was obvious that it was a complex piece of work in science and technology, and scientific research work is seeking truth from facts which means we should have our feet planted on solid ground. Hence, we should first complete our investigations on the available materials, including the skills that we could master to make and create the conditions for designing the equipment and carrying out various plans.

    Zhang: at the end of the 1950s, the work conditions in the archaeological institute were very poor, and there were few publications on humanity and culture and nearly no materials on natural science. There were even fewer materials related to carbon-14 chronology. Under these conditions, how did you combine your efforts and the need of our country to create China's first carbon-14 chronology laboratory? 

    Qiu: carbon-14 is a radioactive isotope, as a result of the interaction between cosmic rays and the atmosphere. The highest content of it accounts for one per one trillion in atmosphere. Radioactive energy is low, and its strength is also very weak, so it belongs to the ray that is the most difficult to detect. Besides, it will require more accuracy when used for dating. Technologies that are used in the laboratory can be divided into radioactive screen technology, high vacuum technology, R&D and manufacture of the detector, R&D and manufacture of electronic instruments, preparation of chemical samples, etc. Of course, we took detecting the radioactivity in carbon-14 and adopted the most advanced technology as our target to make our work plan.

Based on the ability of processing and materials that we could get domestically, we designed the special count tubes for detecting carbon-14, including the proportional counter tube for filling carbon-14 gas and Geiger count tube for removing the influences of cosmic rays. The factory just processed the shell of the tube but installation and performance testing was our business. There were no factories that were able to manufacture the instruments that we needed and the wireless components on the market were insufficient. Starting from a piece of silicon steel, and winding transformer, we made the instruments one by one ourselves. Then, we collected them together to form a whole set to experiment with. The trial manufacturing tube and preparation of carbon-14 sample gas’ count tube were all needed to build a high vacuum system, which needed to be designed and established by us. In a word, we had to learn something that we didn’t understand. From electrical engineering, metal processing, welding, to the manufacture of glass, etc, we should master them all and then we could handle them very skillfully. Many things were done by us, such as finding instruments, finding the processing factories and purchasing the reagents. We tested our equipment many times until they met our requirements.

In 1962, we had an overall trial operation. From the results of the trial, we could say the establishment of the lab had been completed. However, because of materials and some other aspects, the background of the count tubes was too high, the effective count rate was very low, and statistical errors in detecting the dates was too great. We redesigned the count tubes and improved the shielding room without any hesitation; we turned the samples into acetylene gas, which improved the content of carbon (under the situation that other conditions didn’t change) in the gas sample which the count tube was filled with. In this way, in 1965, we lowered the background of the count tubes and improved the effective count rate, which reduced statistical errors of detecting the dates and reached a satisfactory level.

The comparison between China’s carbon standard in sugars and the earliest international standards that China participated in

    Zhang: Mr. Qiu, you are not only the person who first introduced carbon-14 dating methods domestically, but also the person who then lead the development of domestic carbon-14 chronology. For example, between 1970 and 1980, your improvements in the research of carbon-14 dating techniques were responsible for the establishment of China’s carbon standard in sugar. China’s carbon standard in sugar was another generation of standardized carbon materials followed by American oxalic acid, Australian saccharose, Vienna starch, and some other international standards, which reflected the strength and research level of Chinese carbon-14 chronology and also the point that China's carbon-14 chronology went out to the world. China's carbon standard in sugar won third prize in national technical progress in the 1980s.

    Qiu: in 1975, Deng Xiaoping was on the political stage again and presided over the work of the state department, so the domestic situation became much better. The Chinese Academy of Sciences, Ministry of Metallurgical Industry and the Ministry of Geology and Minerals decided to hold a national meeting about the application of isotopes and it was the organizer of the meeting who informed representatives of the carbon-14 laboratory at the archaeological institute to participate in it. The party committee considered this to be a business conference and had to invite me, he decided to assign another committee of the Party as the official representative to go with me. On our way to Guiyang, that committee of the Party found some excuse to go somewhere else, so I had to attend it as a nonvoting delegate. The meeting delivered an academic exchange, and the meeting decided to establish national standards for each isotope. Conference organizers and peers trusted the mission to use the modern carbon standard to build a carbon-14 dating laboratory at the Archaeological Institute. Besides, it asked the Geographical and Chemical Institute of Beijing University and Chinese Academy of Sciences to participate in this work. After coming back to Beijing, I was entrusted to take the task to the leaders of our institute. As it was a national task, so the propaganda team had no choice but to accept.

Then, we did a full investigation on the standards that had been set up. The original standard and material that the international community adopted was oxalate, which was stored at the American National Bureau of Standards, which was made by referring to the radioactive calibration of wood in 1985. Laboratories from all countries in the world purchased it from the American National Bureau of Standards, and its price was very high. Besides, it was due to run out. Some countries demarcated cane sugar, starch, calibration carbonate etc, as secondary materials by contrasting them with the radioactivity of American oxalic acid. According to the domestic reality, I chose to analyze pure sugar and turn it into carbon, namely sugar carbon, by destructive distillation. As a kind of standard material, its features include: (1) sugar carbon was pure carbon, and the isotopes are well-distributed by grinding and mixing well; (2) the level of carbon-14 is similar to modern carbon; (3) it is easy for conventional chemical preparation; (4) it is not easy for the fractional distillation of isotopes during preparation; (5) it is convenient to pack separately and protect, and it is difficult to contaminate. About the performances, (3) and (4) are much better than international standard materials.

Even so, it was much more difficult to implement. It not only needed careful planning but also needed the support of all our workers. Just at this moment, the leaders recommended me to participate in a national scientific conference. During this period, I took this up with comrades from the Department of Commerce and requested tons of ordinary cane sugar. Then, I asked the Shanghai reagent factory to purify it to get pure sugar. Again, it was made in to sugar carbon by destructive distillation. At last, they packed it separately, and a bottle contained 100 grams, 1000 bottles in total. It could meet the needs of the carbon-14 national labs for ten years.

As long as standard materials have been solved, next, it needed to accurately demarcate radioactivity which was much more difficult. We used the oxalic acid standard from the U.S. Bureau of Standards and Australian sugar standards. Besides, we also collected the wood from the northeast forest and Tibet though the weather dept of the Chinese Academy of Sciences and found wood that was cut in 1850. Then, we smashed them and mixed it. At last, we distributed them with American oxalic acid and Australia sucrose, glucose carbon to three labs to detect together. We invited the isotope lab of the Institute of Geology of the Chinese Academy of Sciences to detect the value of carbon-13 in all samples. At last, the values from all of the labs were collected together for treatment, and got the ratio of radioactivity of sugar carbon to the international modern standard of 1.362 1 0.0020.  

In 1981, at the first national carbon-14 academic conference, as the representative of the standards working group，Cai Lianzhen gave an academic report on building the standard for carbon sugar. After the research and review of it, the representatives participating in the conference thought: the materials that had been chosen were suitable, as the carbon sugar was easy to preserve and prepare; the Radioactive rate was moderate, and the calibration accuracy of the sugar carbon reached the standard requirement; he recommended the above sugar carbon as a unified Modern China carbon standard for trial, and named it "China’s carbon standard in sugars."

After 4 years of trials in dozens of domestic laboratories, at the third national carbon-14 academic conference in 1985, representatives who participated in the conference gave it high praise. At the same time, the sugar carbon had been sent to six famous carbon-14 laboratories including the U.S., France, Switzerland, the Soviet Union, and Australia and so on for comparison detection. Then, the results of the mean value were fully consistent with our calibration. In 1987, the China National Bureau of Standards confirmed that "China sugar carbon" was the unified modern standard of carbon-14 used to detect dates, its number and name: GSBA650001-87, China carbon standard in sugars. In 1989, it won the third prize for national technical progress.

    Zhang: the thing that people who deal with the dates care most about is the reliability and precision of the data, and the contrast with the international standards made people think it was a kind of calibration of reliability and precision. Therefore, this kind of comparison often caused wide concern. From the materials, in the 1980s, around the calibration of Chinese carbon standard in sugar, you presided over the 6 famous international comparisons that carbon-14 laboratories participated in, which were the earliest comparisons that the Chinese were involved in and were highly precise comparisons. What was it about the specific situation? What about its significance?

    Qiu: since 1981, we sent the sugar carbon to the six famous international laboratories and requested them to detect the ratio of sugar carbon to international standards. The results that we received:  (1) in 1981, the Australian National University, in a message of congratulations to our first National Carbon-14 conference, Polach of the carbon-14 laboratory said that American oxalic acid standard and the Australia NB S sucrose standards were all good when compared to the detection and comparison of Chinese carbon standard in sugar, and he recommended it could be China's national standard for modern carbon and sent to other international laboratories. According to his results, the initial ratio of sugar carbon to international standards was R=1.352-+0.005. (2) In 1983, the result from Delibrias the French radioactive Center (Gif) was R = 1.362 +0.005. (3) In 1984, the result from Oeschger at the Switzerland University of Bern (B) was R = 1.365 ± 0.0020. (4) In 1985, at the Institute of Geology of the USSR Academy of Sciences, the result from number of data was R = 1.360 1 0.002. (5) In 1986, the result from Stuiver in the Isotope Laboratory of the Quaternary research Center at the University of Washington, Seattle, USA, was R = 1.372310.00120. (6) the result from the Geological Dating Laboratory at the Department of Geography of the Soviet University of Leningrad was R=1.351士0.004.

According to the 6 labs, we get contrasting values, such as the arithmetic average, and if we calculated the standard statistical deviation of discrete data by using Gaussian distribution the average value was R=1.360 1 0.0080.

It proved that the testing level of our carbon-14 had reached advanced international levels.

The backing that Carbon-14 Dating had on the Study of Prehistoric Archeology

    Zhang: the greatest contribution that carbon-14 dating has made to Chinese archaeology has pushed and deepened prehistoric archaeology research. Until the 1990s, based on the study of more than 2000 carbon-14 data sets, we established the framework for Chinese prehistoric archaeology since the late Paleolithic era.  

    Qiu: the focus of archaeology before carbon-14 dating methods was mainly on prehistoric archaeological chronology. Before the use of carbon-14 dating methods, archaeologists could not make correct judgments on the absolute dates of all kinds of prehistoric cultures. Prehistoric chronology was almost based on subjective judgment and inference. Xianai pointed out: “great changes have occurred in chronology in many places around the world because of carbon-14 dating methods, and people called it ‘the revolution of radioactive carbon’ ”. Also, in our country, because of the adoption of carbon-14 dating methods, it framed the relationship of Neolithic cultures in time and in different places, made Chinese Neolithic archaeology enter into a new era because we had the exact sequence of dates. Archaeologists, at some archaeological sites such as Zhenpi rock, were unable to recognize and evaluate it without the carbon-14 dating method.  

    Zhang: can you tell us which aspects of the research on carbon-14 chronology have reached an international level?

    Qiu: as I said, the establishment and comparison of Chinese carbon standards in sugar proved that our carbon-14 detecting level had reached international levels. The reliability of the framework of Chinese prehistoric archaeology since the later Paleolithic era received recognition from the archaeological world. Now, adopting the method of testing a series of samples can reduce dating errors which has been put into practice on the chronology project of the Xia-Shang-Zhou dynasty and was very successful. Besides, it is being applied to Chinese Civilization project, which is unique in the world. Of course, it is related to the dense and continuous ancient cultural sites in China, careful archaeological field work, which are suitable for developing the carbon-14 dating method and be combined with the application of a series of archaeological samples.

    Zhang: professionals think carbon-14 dating is a hard science, which reflects the difficulty and depth of this subject. But, to you, the area you serve it is a practical subject. Basic research often has some difficulties, applied research is tantamount to cross-disciplinary. How did you combine them together?

    Qiu: the research on carbon-14 dating is applied science, of course, but about the research itself, we need basic knowledge and the experiment technology of nuclear physics and radioactive chemistry, we need to master detection technology when developing the detector, we need to develop electronic circuits to amplify signals and analysis technology, we need to master chemical preparation technology such as gas or benzene in liquids which can be the gas used in the  detector or the solvent in liquid glistening pool, and at last we need to master the strict relative measurement technology by which we can get carbon-14 dates and we can get the dates through dendrochronology correction. Now, you can purchase the whole set of instruments and equipment when establishing a carbon-14 dating laboratory and it will be ok if it can be operated correctly. Well, all of these were prepared by ourselves when we built the carbon-14 dating laboratory. For high accuracy measurements, we should pay attention to error analysis. With the dating technique, we can build the archaeological chronology and provide more effective services to archaeological research by combining it with the field of archaeology. We can say carbon-14 archaeological chronology is the cross-discipline between nuclear detection technology and archaeology. Therefore, the more we know about the field of archaeology the better the dating service we can offer.  

    Zhang: Your career has not been plain. In the process of the pursuit of the truth, you came across many problems, but the thing that scientific research stresses most is seeking truth from facts. What made you dare to stand up, and boldly explore truth during the decades of your academic career? Can you talk a little about you tough experiences.

    Qiu: our generation has experienced a lot of ups and downs, especially the "right" experience. Looking back to the recent 50 years of history we went through many challenges and even fierce trouble, and we still could do some things for our country and our Party. The reason that I didn’t go in the wrong direction is that I always adhere to some principles.

First, I was a university student after the founding of the new China, and received the party's education. Although I didn’t read many books on Marx and Lenin, my attitude to study was very serious. In 1957, I was classified as "Rightist" because I studied the Eight Big Decisions and spirit of report the on chairman Mao's dealings with the contradictions among the people very seriously. At that time, the organizations of anti-rightists put forward that we should distinguish the two different conflicts and shouldn’t enlarge the anti-rightist campaign. Besides, they also stressed studying Marxism-Leninism in practice. It was a shock when I was classified as "Right". During the 22 years since then, everyone could see what I did. However, I didn’t lose confidence, on the contrary, I studied Marxism-Leninism harder, studied the history of the Soviet party to explore their laws of history. I thought the outcome of the 20th Central Committee of the Soviet Communist Party was wrong, revealing past historical facts should be worthy of study. From the above, we can see that it was not my fault that I was classified as a "Rightist", and I didn’t completely lose the opportunity to repay our country, which was worth cheering. Although I had to overcome economic difficulties in my daily life, I had to confess and admit my mistakes against my will, which disturbed and hindered the work very much. Not long after the beginning of the "cultural revolution", I judged that it wouldn’t last for long. I was sure that the mistakes of the anti-rightist campaign might be corrected after the "cultural revolution". In fact, the problems of the "Right" were the problems of intellectuals, so how to build a socialist construction without solving them? 

Second, for scientific research, we fully recognize that science must be realistic without any impetuous and luck. In the institute of atomic energy, with Qian Sanqiang as the director, a group of scientists came from abroad and led the young to do research; in the archaeological institute, we met some good archaeologists like Xianai, whose good style of study influenced me a lot. The reason that I could be a self-made man and built the first national carbon-14 dating laboratory was that we implemented the theory with practice and treated the work seriously. Under the background of the "Great Leap Forward", everywhere was full of impetuous and formalism such as everyone engaging in ultrasound, which wasted a lot of materials. However, we weren’t disturbed at all. We tried our best to create conditions for our research. Based on our own skills, and the skills and the materials that we mastered, we made out plans, and produced the equipment and instruments. We overcame many difficulties until we reached the final goal.

The research and application of carbon-14 chronology in the Xia-Shang-Zhou chronology project

    Zhang: in the mid-1990s, the largest scientific research project – “the project of Xia-Shang-Zhou chronology” that was a “key research subject" of the 9^th five year plan, made carbon-14 chronology move up a notch. As one of the chief scientists who were appointed by the State Council for archeology, astronomy, history, and carbon-14 dating, how did you conduct the process of the project? Can you introduce the role that carbon-14 dating played in the project of Xia-Shang-Zhou chronology?

    Qiu: in 1995, at the International Conference on Yanshi’s Shang Culture, we released an essay that adopted the method for archaeological samples which could reduce the errors in archaeological dating greatly, which provided hope in judging the dates of Wuwang-Wang Keshang. At the end of 1995, the director of the Commission on National Science and Technology put forward the Xia-Shang-Zhou chronology project which could provide a series of samples fpr the dating method.

The carbon-14 dating method of an archaeological series of samples was to turn the relative age sequence on the level of field of archeology and cultural staging into a highly precise and absolute age sequence. inthis way, we determined the archaeological calendar of events, which reduced the error in dates greatly. Specific steps as follows: (1) collecting the series of samples which contained the carbon were highly related to archaeological age or cultural staging. (2) After elaborate preparation of samples, we got accurate and reliable carbon-14 dating data, and it was consistent with reality. (3) Making the best of archaeological information, matching data of carbon-14 dates in a series of samples with the curve of highly precise dendrochronology correction to make calendars of the archaeological connotation. (4) After the common research on all of the results from every series of samples by matching carbon-14 dating from experts and archaeologists, we could make out the corresponding table of archaeological dates, or called: the framework of archaeological dates. Now, I will show you some examples:  

First, in the cemetery of the Marquis from the Jin Dynasty, Tianmaqu village, Shanxi province, the M8 was the grave of Jinxian Marquis-Su in which 16 rhymes were inscribed with 355 characters that recorded the 33 years of King Wei was found. It was obviously consistent with the record in the Historical Records • Jin Family which said Jinxian Marquis-Su died in the sixth year of King Zhouxuan (812 B.C.). Obviously, 33 years of King Wei are not the 33 years of King Zhouxuan, referring to the 33 years of King Li when Jinxian Marquis-Su was alive. Therefore, King Li had been King for more than 33 years which proved the 37 years of King Li was correctly recorded in the Historical Records • Jin Family.

Second, in the relics found in Yangxi Shanxi province in 1997, probing area T1 with 975CM was made up of a series of stratigraphic units, the bottom H18 was an ash pit and belonged to the culture of the late Zhou dynasty. Above the H18, it was the fourth floor T1 belonging to the early western Zhou dynasty. This provided the basis for ideal archaeological formation for dividing the boundary between the Shang dynasty and the Zhou dynasty. The years of Wuwang-Keshang should be contained in these dates. Upper and lower strata all have samples for dating, and the samples that made up the stratum showed the dates of the boundary between the Shang dynasty and the Zhou dynasty was from 1050 to1020.

Third, the Yin Dynasty ruins in Anyang city, Henan province, I which the culture was divided into four periods. The range of dates of the Yin Dynasty ruins was detected through a series of samples of human bone from all graves. If we take the series of burial tombs from the Yin Dynasty ruins and a series of burial tombs from the Western Zhou Dynasty in Liulihe as a series, the dates of the boundary was consistent with the dates of Wuwang-Keshang.

Fourth, the culture of the Luoda temple and the culture of the Erligang have overlying relationships in date. According to the carbon-14 dating of the series of recent samples, it indicated that the first stage of the lower layer was dated to about 1500 B.C. The wall of the Shang dynasty in Zhengzhou was not earlier than the first stage of the lower layer of Erligang. Therefore, the establishment of the Shang dynasty’s city was not earlier than 1500 B.C.

Fifth, according to the determination of a series of samples from the Erlitou site, the boundary between the culture of Erlitou and the culture of Erligang was dated to about 1500 B.C, which is similar to the boundary between the culture of Luoda temple and the culture of Erligang.

Sixth, according to the results of the data from a series of samples from the new IMS site, late culture of longshan, Henan province, the early and late culture of Xinzhai and the culture of Erlitou. The first stage of Erlitou was not earlier than 1750 B.C and the culture of Erlitou was not earlier than 1850 B.C.

The dating framework for the Zhou dynasty, Xia dynasty and Shang dynasty was formed by combining the archaeological timeline according to a series of archaeological samples from the western Zhou dynasty, Xia dynasty and Shang dynasty with the dates that astronomy presumed based on the eclipse recorded on Zaidan and Binzu oracle bone inscriptions in the first year of King Huo together. We thought the errors in the dates after Pangeng wouldn’t be large. Before it, two dates of the Shang dynasty’s city couldn’t happen in the dates of the same King and the boundary between the Xia dynasty and the Zhou Dynasty also needed further research.

The role that Carbon-14 dating plays in research exploring the Origin of Civilization

    Zhang: in the 1990s, the research and application of the high-profile method of a high precision series of samples gave carbon-14 chronology a new leap forward in the international carbon-14 field. Besides, the research of carbon-14 dating no longer merely stayed on the stage from the late Paleolithic period to the Neolithic period and could take solid steps in the period when ancient civilization formed or even as it was developing. You are the first one who put the method of a series of samples into the research of domestic archaeological chronology. Can you give us an outlook about the method for a series of samples in carbon-14 dating during the research of exploring the origins of ancient civilization since the project of Xia-Shang-Zhou?

    Qiu: since the method of a series of samples was applied to the project of Xia-Shang-Zhou chronology successfully, naturally it can be applied to project of exploring the origin of ancient civilization. Archaeological discoveries and research content that began from the new Stone Age are very rich and the cultural lineage also has some foundation. Based on the chronology  of the Xia-Shang-Zhou project, pushing the archaeological timeline to more ancient times can be done completely by applying the method of a series of samples. The key is to collect a qualified series of samples from every culture together with archaeologists to detect the carbon-14 data carefully and with high precision, and then research by use dendrochronology correction with high precision. For example: the archaeological timeline we got by using the OxCal program and that is to say the coordinate axis of time can provide the formation of ancient civilizations. I think that from Erlitou-Xinzhai-Wangchenggang, this period can be made clear but it needs more meticulous detection. Next, the key is to make clear the genealogy of the Tao temple site and get a series of qualified samples, which can create a breakthrough in the Origin of Civilization.  

Extension of related research

    Zhang: which other aspects did you study in addition to carbon-14 dating research?

    Qiu: In line with archaeological research, I also solved the following questions.

First, the determination of white ash which was often found in the Neolithic sites, we didn’t know what it was? Was it lime? It bothered the archaeological world for a long time. We knew its main content was calcium carbonate after chemical analysis but we didn’t know without burning it.

Based on our analysis, we judged that it must contain carbon-14 if it was formed by burning and the carbon-14 could be used to detect the dates. Therefore, we collected some samples and detected the dates. The results proved that it was lime that was burned over 4000 years ago. In this way, it solved the archaeological problem that was also a big challenge in architectural history. In the house on site of Qinan Dadi bay in Gansu province, the materials which were used to pave the surface were Liaojiang rock.

Second, the identification and dating of materials for iron making. When coal was discovered on the Tiesheng ditch site in Gong County, Henan province, someone thought that the coal had been used as fuel for iron making in the Han dynasty and also wrote it in the history of chemistry. However, after using the carbon-14 method to detect the iron materials and iron tools, we found that the coal wasn’t used as fuel for iron making until the Song dynasty and people used carboligni as fuel for iron making before the Song dynasty.

There was always some limestone which was added into mineral aggregate when making iron, which facilitated the materials flow. Limestone was turned into calcium oxide (slag) due to the high temperature, which was alkaline and took in atmospheric carbon dioxide, so it could be used for dating. We once detected carbon dioxide which was taken from iron slag the the Jinnanbao ancient site in Chicheng county, Hebei province, and the dates were 964士60 B.C , and dated to 1020 B.C to 1170 B.C after dendrochronology correction, equivalent to the era of the Liao and Jin dynasties.

Third, about the dating detection at caves sites in the limestone area, in the southern limestone area, some early cave sites and cowry sites were discovered, which main forms of economy were fishing and hunting, and sometimes collection. Among the stone tools, some were made through hitting and some were made though grinding. Besides, there are some potteries with the main rope lines printed on them, which were made of original coarse sand. It belonged to a time more than 8000 to 9000 years ago, or even more than 10000 years. Some archaeologists didn’t think it was dated to so early era, and they suspected that it was the result of area specimens of limestone being influenced by the dead carbon. In the 1970s, comrades from the laboratory of Peking University and me went to Guilin to investigate. Through detection and research, we found that the terrestrial specimen was not affected by the dead carbon, while the aquatic animals and plants would be affected by it to a different degree. Generally, the dates of shells were older, about 1000 to 2000 years, which was reasonable. Terrestrial plants get carbon dioxide through photosynthesis while under the water, for the water dissolves limestone to produce the dead carbon, the carbon-14 dates of aquatic specimens is relatively older. At that moment, we also defined the era of earthenware in the Chanpi rock as more than 9000 years ago. Then, research which matched the excavation also proved that. 

Fourth, it is the research in human diet. We had the advantage of using samples of human bone to detect the dates, and analyzed the carbon-13 isotope from the collagen in bone to research human staple foods in the Neolithic age. The north used millet as a staple food while the south used rice, which was consistent with ancient agriculture. In this way, I developed a new field which applied the isotope into the research of ancient human recipes.

Experience from scientific research

    Zhang: scientific research achievements are often comforting and exciting, but the process of exploration was unavoidably dull and boring. Most of your life was in the laboratory that is not large in the yard of the archaeological institute. Can you talk about your feelings?

    Qiu: Marx once said that in the scientific field, you should have the spirit of going to hell and that only the people that didn’t fear challenges could get success in the scientific field. I was just an ordinary scientist and should fulfill my duties. The people who do scientific research should withstand loneliness. Besides, we should “not regret when we were thin and pallid from scientific research”. By only concentrating our energies in to scientific research, can we can get some achievements. I always think that all of my work conditions and the cost of living are provided by our country and our people. Therefore, I should try my best to repay our country and our people. Moreover, scientific research is not boring, and we have plans and steps for discovering problems to research problems to solving problems. Every time, when we achieve something, it was the happiest time and we would feel extremely pleased and excited. Of course, we wouldn’t be complacent and stop at that, on the contrary, we would summarize the lesson and move on for excellence as we still need to be practical and realistic. Research needs correct judgment, and cannot follow the herd and impetuous. As long as the judgment is correct, innovative ideas and research materials are rich, and the basis is abundant, you don’t have to worry about the opposite. We shouldn’t always think about how many essays we should write. We should bear the spirit of “using a decade to grind a sword, and write essays without any empty sentences”. “Tartness of treasure sword came from hard grind, and the fragrance of plum flower came from the harsh cold”; it was the good style of study that our workers of scientific research should remember. Let us encourage each other in our endeavors.

     Translated by Li Junwei.

Editor: Wang Daohang