The three-day first meeting of the European branch of the Chinese Society for Science and Technology came to an end on the evening of December 27, 1907, and the meeting announced the formal establishment of the European branch of the Chinese Society for Science and Technology, formulated the constitution and organizational structure, established the development goals and plans of the society, clarified the responsibilities of each branch, and elected the main leaders of the society. As the first scientist in modern China who was widely recognized and widely praised by the Western academic community, Sun Yuanqi was elected president of the society with a high vote without any suspense.

After the meeting, the participants began to return to their respective schools, but as the main leaders of the society, they could not leave, and the next things were more complicated: cleaning up and summarizing the use of conference funds, and formulating the budget for the beginning of the year; Collect the articles of association and contact information of each society, print them into a booklet, and distribute them to all members, and keep a few copies to send to the American and Japanese chapters later; Prepare for the establishment of the editorial department of the journal of the society, and prepare for the printing and publication of the journal "China Science and Technology......

Sun Yuanqi's vacation was only three months, and since he left Wuhan in mid-November, he is now halfway. In the remaining month and a half, we will have to cross the Atlantic, the American continent, and the Pacific Ocean, and there will not be much wealth at all. Therefore, after explaining to the members of the society who called for the establishment of a branch of the society in major newspapers and periodicals in the United States, Canada, and Japan, he hurriedly stepped on a passenger ship to the United States and rushed to MIT and Yale University. There, there is a large group of colleagues looking forward to it.

To make a long story short, six days later, Sun Yuanqi arrived in New York without incident. Because of the urgency, he could not take a break after a long trip, so he went to Yale University accompanied by a colleague.

Since leaving the United States in 1904, Sun Yuanqi has not been in the Elemental Laboratory for more than three years. In addition to doing some experiments according to Sun Yuanqi's instructions, they also used particle accelerators to make many outstanding achievements, such as the synthesis of the element astatine with atomic number 85 by bombarding the bismuth target with α particles, the element francium with atomic number 87 in the decay product of actinium-227, and the isotopes of a variety of known elements were made with particle accelerators. As a result of these achievements, the reputation of this laboratory is comparable to that of the established Cavendish Laboratory in the United Kingdom after only six or seven years of establishment.

When the laboratory colleagues heard that Sun Yuan was coming, they all gave up their annual leave and gathered in the conference room. As soon as Sun Yuanqi entered the door, warm applause swept in.

After the greetings, Professor Dracula, the director of the laboratory in the United States, began to report on the progress of the work in the past few years, and then he asked Johnson bluntly, what is the work plan of the laboratory in the next few years? ”

Although he has been gone for several years, he still serves as the Chinese director of the laboratory. I'd like to hear your plans first. ”

Professor Dracula was not polite, and took out a page and handed it over the past few years, and the laboratory has combined with your description of the periodic table to test the various elements that have been made. After a series of rigorous tests, at least 3 elements have not been detected before uranium, so we want to draw up a reasonable experimental plan in the future, increase experimental efforts, and strictly test, and strive to complete the periodic table. These are some of the experimental protocols that we have drawn up roughly, so please take a look at them."

As early as 1899, when Sun Yuanqi wrote the booklet "From Atoms, Atomic Structures to Elements, the Periodic Table, Molecules and the Nature of Chemical Reactions", which was later referred to as "Principles of Chemistry", he "designed" the experiment of the British physicist Moselle for three years, proving that the frequency of the spectral characteristic line and the atomic number of the element have an intrinsic relationship, and it was clear that the basis of the periodic law is not the atomic weight, but the atomic number. After this experiment was rigorously confirmed, it was quickly accepted by the academic community. At the same time, the Element Lab uses this method to present a gap in the periodic table.

Sun Yuanqi took the paper, and it turned out that the vacant were the three elements with atomic numbers 61, 72, and 75. Because he often turns over "History of the Elements", Sun Yuanqi naturally has not been used for these elements until now:

The two elements with atomic number 72 and 75 are naturally occurring, but in order to think about them, in addition to the right method and careful analysis, the key depends on luck.

For example, the element rhenium with atomic number 75 was predicted as early as Mendeleev when he established the periodic system, and scientists are also committed to finding traces of it from manganese ore, platinum ore and niobium iron ore, but no one has officially made it official for decades. In 1922, Nordak, who had just graduated from the University of Berlin, set this element as the scientific goal of scientific research, and with the help of Tucker and Berg, he carefully fractionated the ore that might contain this new element for three years, and finally cultivated it into a positive fruit, and named it rhenium after the name of the Rhine. - Of course, in addition to the new element, Nodak also has one more gain: he has won Tucker's heart. In 1926, they were officially married, and after their marriage, the two continued to study rhenium and various other elements.

Another example is the element hafnium with atomic number 72.

Hafnium is very present in the crust and often coexists with zirconium without a separate ore. In the early days, chemists generally classified hafnium as rare earth elements, so everyone focused on rare earth element minerals, so nothing was found. In fact, according to the new theory proposed by Sun Yuanqi, hafnium should belong to the same group as titanium and zirconium, and should be found from ores containing zirconium and titanium. In fact, in 1923 the Swedish chemist Hevesiy and the Dutch physicist Koster identified the element in zircon, naming it hafnium in honor of the location of the element, Copenhagen, the capital of Denmark.

This element is mostly found in zircon from Norway and Greenland, and is found in small amounts in zircon from other places. If you can't get the right zircon, no matter how much effort you spend, it's a blind man lighting a lamp - in vain. Therefore, scientific research depends on luck.

Now it's time to talk about promethium, an element with atomic number 61.

Historically, promethium is the second chemical element artificially produced after technetium. Prior to this, people were looking for this "long-awaited" lanthanide member through various methods, and all kinds of means were unsuccessful, and it was once called the "lost element". In 1926, not long ago, the Nodak couple who had just rhenium element, in spite of the newlywed Yan'er, in order to find traces of promethium, used all possible technologies at that time to analyze 15 minerals expected to contain promethium, and processed 100 kilograms of rare earths, but they could not detect it. In the end, the chemists were at the end of their rope and had no choice but to ask physicists to come out.

The first method that physicists came up with was from cyclotrons. The original protocol was to bombard the neodymium target with accelerated deuterium nuclei, which produced an isotope of element 61 through a nuclear reaction. The results were, but they were based only on radiometric data, and there were mixed reviews about the purity of the neodymium targets and their identification methods.

The next method that physicists came up with was nuclear fission.

One of the greatest in the 40s of the 20th century was the fission of uranium. Uranium-235 splits into two fragments under the action of slow neutrons, each of which is an isotope of one of the elements in the periodic table. Various isotopes of more than 30 elements, from zinc to gadolinium, can be produced by the nuclear fission method, and the promethium element obtained by this method is about 3% of the total fission products. However, it is difficult to extract this 3% of element 61 by ordinary chemical methods.

That's where chemists come in. Mariinsky and others in the United States innovatively applied a new chemical technology, ion exchange chromatography, to separate the fission products of uranium, and finally isolated this fascinating element in 1945.

Is ion-exchange chromatography a technique? Sun Yuanqi, who is a master's degree in physics, naturally does not, and the "History of the Elements" for middle school students will not say. Of course, even if it is said in the book, Sun Yuanqi is still helpless: ion exchange chromatography requires the use of ion exchange resin, and who should be used to produce this ion exchange resin? Still can't help it. Sun Yuanqi can't do anything, and it is estimated that the colleagues in the Elemental Laboratory will not be able to do it in the next ten or twenty years. Therefore, promethium can only wait for future technological development.

Sun Yuanqi looked at the paper handed by Professor Dracula, read it, and then commented that about the element with atomic number 61, you proposed to bombard the neodymium target with an accelerated deuterium nucleus, which is very correct, after all, the technetium element is like this. However, this method yields too little new material, so I suggest that you treat this work as a long-term task and not rush it. ”

Everyone is a little puzzled: why not rush at the moment? 10,000 years is too long, but it's not good to ask directly.

Sun Yuanqi went on to say that as for the element with atomic number 72, you think that rare earth element minerals should be analyzed, which is a bit inappropriate. I think this new element should belong to the same group as titanium and zirconium, and should be found in zirconium- and titanium-containing ores, rather than rare earth element minerals. Of course, the associated elements of the ore may be different from place to place, so it is best to collect all the minerals produced in each place. ”

Of course, it is difficult to say that "everyone should look for zircon from Norway and Greenland", otherwise it would be "wise and almost demonic", which should arouse suspicion.

Colleagues in the laboratory hurriedly put pen to paper and wrote down Sun Yuanqi's suggestion.

Sun Yuanqi also said that the element with atomic number 75, you plan to analyze molybdenumite, rare earth ore and niobium-tantalum ore, which should be roughly the same. However, I suspect that the content of this element is too low, and it will have to be very detailed, and it will be a lot of work. ”

The content of rhenium in nature is indeed very low, and the Nodaks and others finally found rhenium in platinum ore under the guidance of the periodic law of the elements, through the analysis of more than 1,800 minerals.

Professor Dracula nodded: In the course of the first few elements, we have cultivated a patient and meticulous working atmosphere in the laboratory, and as long as we go in the right direction, then we will definitely achieve our goals"

The surrounding colleagues nodded in agreement.

"Professor Johnson, we would very much like to hear your suggestions for the future work of the laboratory." Professor Dracula said.

Sun Yuanqi pondered for a moment, and then said I think that the elements before the uranium element were basically posted, and the research direction of the element laboratory should be divided into two categories, one is to study the preparation method of known elements, and the other is to study transuranic elements. ”