The Discovery of Radium

I could tell you many things about radium and radioactivity and it would take a long time. But as we can not do that, I shall only give you a short account of my early work about radium. Radium is no more a baby, it is more than twenty years old, but the conditions of the discovery were somewhat peculiar, and so it is always of interest to remember them and to explain them.

关于镭和放射性，我可以告诉你们许多事情，那要讲很长时间。但我们没法那样做，所以我只简短地讲讲我早年关于镭的工作。镭已经不是婴儿了，它已经二十多岁了；不过它被发现时的情形有些特别，所以回忆一下、解释一下，总是有意思的。

We must go back to the year 1897. Professor Curie and I worked at that time in the laboratory of the school of Physics and Chemistry where Professor Curie held his lectures. I was engaged in some work on uranium rays which had been discovered two years before by Professor Becquerel. I shall tell you how these uranium rays may be detected. If you take a photographic plate and wrap it in black paper and then on this plate, protected from ordinary light, put some uranium salt and leave it a day, and the next day the plate is developed, you notice on the plate a black spot at the place where the uranium salt was. This spot has been made by special rays which are given out by the uranium and are able to make an impression on the plate in the same way as ordinary light. You can also test those rays in another way, by placing them on an electroscope. You know what an electroscope is. If you charge it, you can keep it charged several hours and more, unless uranium salts are placed near to it. But if this is the case the electroscope loses its charge and the gold or aluminum leaf falls gradually in a progressive way. The speed with which the leaf moves may be used as a measure of the intensity of the rays; the greater the speed, the greater the intensity.

我们得回到1897年。那时居里教授和我在物理化学学校的实验室里工作，居里教授在那里讲课。我当时在研究铀射线，那是两年前由贝克勒尔教授发现的。我来告诉你们怎样检测这种铀射线。取一张照相底片，用黑纸包好，在这张不受普通光照射的底片上放一些铀盐，放上一天，第二天把底片冲洗出来，你就会看到底片上放铀盐的地方有一个黑斑。这个黑斑是由铀放出的一种特殊射线造成的，它能像普通的光一样在底片上留下印记。你们也可以用另一种方法检验这些射线：把它们放到验电器上。你们知道验电器是什么。给它充上电，它可以保持带电好几个小时甚至更久，除非把铀盐放在它旁边。但如果放了铀盐，验电器就会失去电荷，金箔或铝箔会一点一点地、渐渐地落下来。箔片移动的速度，可以用来衡量射线的强度：速度越快，强度越大。

I spent some time in studying the way of making good measurements of the uranium rays, and then I wanted to know if there were other elements, giving out rays of the same kind. So I took up a work about all known elements, and their compounds and found that uranium compounds are active and also all thorium compounds, but other elements were not found active, nor were their compounds. As for the uranium and thorium compounds, I found that they were active in proportion to their uranium or thorium content. The more uranium or thorium, the greater the activity, the activity being an atomic property of the elements, uranium and thorium.

我花了一些时间研究怎样把铀射线测量好，然后我想知道，是否还有别的元素也放出同一类射线。于是我着手研究所有已知的元素及其化合物，发现铀的化合物有放射性，钍的所有化合物也都有，而其他元素都没有发现放射性，它们的化合物也没有。至于铀和钍的化合物，我发现它们的放射性与其中铀或钍的含量成正比。铀或钍越多，放射性就越强；放射性是铀和钍这两种元素的原子性质。

Then I took up measurements of minerals and I found that several of those which contain uranium or thorium or both were active. But then the activity was not what I could expect, it was greater than for uranium or thorium compounds like the oxides which are almost entirely composed of these elements. Then I thought that there should be in the minerals some unknown element having a much greater radioactivity than uranium or thorium. And I wanted to find and to separate that element, and I settled to that work with Professor Curie. We thought it would be done in several weeks or months, but it was not so. It took many years of hard work to finish that task. There was not one new element, there were several of them. But the most important is radium which could be separated in a pure state.

接着我开始测量矿物，发现好几种含铀、含钍或两者都含的矿物有放射性。可这时的放射性不是我所能预料的：它比铀或钍的化合物——比如那些几乎完全由这两种元素组成的氧化物——还要强。于是我想，矿物中一定有某种未知的元素，它的放射性比铀或钍强得多。我想找到它、把它分离出来，便和居里教授一起投入了这项工作。我们以为几个星期或几个月就能完成，结果并非如此。完成这项任务花了许多年的艰苦工作。新元素不止一种，而是好几种。但其中最重要的是镭，它可以被分离成纯净的状态。

All the tests for the separation were done by the method of electrical measurements with some kind of electroscope. We just had to make chemical separations and to examine all products obtained with respect to their activity. The product which retained the radioactivity was considered as that one which had kept the new element; and, as the radioactivity was more strong in some products, we knew that we had succeeded in concentrating the new element. The radioactivity was used in the same way as a spectroscopical test.

所有分离的检验，都是用电学测量的方法、借助某种验电器来完成的。我们只需进行化学分离，再检查所得到的每一种产物的放射性。保留了放射性的那种产物，就被认为是留住了新元素的那一种；而由于有些产物的放射性更强，我们就知道，我们成功地把新元素富集起来了。放射性在这里的用法，和光谱检验一样。

The difficulty was that there is not much radium in a mineral; this we did not know at the beginning. But we now know that there is not even one part of radium in a million parts of good ore. And too, to get a small quantity of pure radium salt, one is obliged to work up a huge quantity of ore. And that was very hard in a laboratory.

困难在于矿物中的镭并不多，这一点我们起初并不知道。但现在我们知道，即使是好矿石，一百万份里也不到一份镭。所以，要得到一点点纯的镭盐，就必须处理大量的矿石。这在实验室里是非常艰难的。

We had not even a good laboratory at that time. We worked in a hangar where there were no improvements, no good chemical arrangements. We had no help, no money. And because of that the work could not go on as it would have done under better conditions. I did myself the numerous crystalizations which were wanted to get the radium salt separated from the barium salt with which it is obtained out of the ore. And in 1902 I finally succeeded in getting pure radium chloride and determining the atomic weight of the new element radium, which is 226 while that of barium is only 137.

那时我们甚至没有一个好的实验室。我们在一间棚屋里工作，那里毫无设施，没有像样的化学装置。我们没有帮手，没有钱。正因为如此，工作不能像在更好的条件下那样进行。为了把镭盐从与它一起从矿石中得到的钡盐里分离出来，需要无数次结晶，这些都是我亲手做的。1902年，我终于得到了纯的氯化镭，测定了新元素镭的原子量：226，而钡的原子量只有137。

Later I could also separate the metal radium, but that was a very difficult work; and, as it is not necessary for the use of radium to have it in this state, it is not generally prepared that way.

后来我还把金属镭也分离了出来，但那是非常困难的工作；而且由于使用镭并不需要它处于这种状态，一般也就不这样制备。

Now, the special interest of radium is in the intensity of its rays which is several million times greater than the uranium rays. And the effects of the rays make the radium so important. If we take a practical point of view, then the most important property of the rays is the production of physiological effects on the cells of the human organism. These effects may be used for the cure of several diseases. Good results have been obtained in many cases. What is considered particularly important is the treatment of cancer. The medical utilization of radium makes it necessary to get that element in sufficient quantities. And so a factory of radium was started to begin with in France, and later in America where a big quantity of ore named carnotite is available. America does produce many grams of radium every year but the price is still very high because the quantity of radium contained in the ore is so small. The radium is more than a hundred thousand times dearer than gold.

镭的特别之处，在于它射线的强度，比铀射线强几百万倍。正是射线的这些效应，使镭如此重要。如果从实用的角度看，射线最重要的性质，是它对人体细胞产生的生理效应。这些效应可以用来治疗好几种疾病。在许多病例中已经取得了良好的效果。人们认为特别重要的是对癌症的治疗。镭在医学上的应用，使得必须获得足够数量的这种元素。于是先在法国、后来在美国办起了镭工厂，美国有大量名为钒钾铀矿的矿石可用。美国每年确实生产好几克镭，但价格依然很高，因为矿石中所含的镭实在太少。镭比黄金贵十万倍以上。

But we must not forget that when radium was discovered no one knew that it would prove useful in hospitals. The work was one of pure science. And this is a proof that scientific work must not be considered from the point of view of the direct usefulness of it. It must be done for itself, for the beauty of science, and then there is always the chance that a scientific discovery may become like the radium a benefit for humanity.

但我们一定不要忘记，镭被发现的时候，谁也不知道它会在医院里派上用场。那是一项纯科学的工作。这就证明，科学工作不应当从它直接的用处来看待。它必须为了它本身、为了科学之美而去做；然后，总有这样的机会：一项科学发现，会像镭一样，成为造福人类的东西。

But science is not rich, it does not dispose of important means, it does not generally meet recognition before the material usefulness of it has been proved. The factories produce many grams of radium every year, but the laboratories have very small quantities. It is the same for my laboratory and I am very grateful to the American women who wish me to have more of radium and give me the opportunity of doing more work with it.

但科学并不富有，它没有多少可支配的财力，在它的实际用处被证明之前，它通常得不到承认。工厂每年生产好几克镭，实验室却只有很少的一点。我的实验室也是如此。我非常感激美国的妇女们，她们希望我拥有更多的镭，给了我用它做更多工作的机会。

The scientific history of radium is beautiful. The properties of the rays have been studied very closely. We know that particles are expelled from radium with a very great velocity near to that of the light. We know that the atoms of radium are destroyed by expulsion of these particles, some of which are atoms of helium. And in that way it has been proved that the radioactive elements are constantly disintegrating and that they produce at the end ordinary elements, principally helium and lead. That is, as you see, a theory of transformation of atoms which are not stable, as was believed before, but may undergo spontaneous changes.

镭的科学史是美的。人们对射线的性质作了非常细致的研究。我们知道，粒子以接近光速的极高速度从镭中射出。我们知道，镭原子因射出这些粒子而毁坏，其中一些粒子是氦原子。由此已经证明，放射性元素在不断地蜕变，最终产生普通的元素，主要是氦和铅。你们看，这就是一种原子转变的理论：原子并不像从前所相信的那样稳定，它们可能发生自发的变化。

Radium is not alone in having these properties. Many having other radioelements are known already, the polonium, the mesothorium, the radiothorium, the actinium. We know also radioactive gases, named emanations. There is a great variety of substances and effects in radioactivity. There is always a vast field left to experimentation and I hope that we may have some beautiful progress in the following years. It is my earnest desire that some of you should carry on this scientific work and keep for your ambition the determination to make a permanent contribution to science.

具有这些性质的并非只有镭。人们已经知道许多别的放射性元素：钋、新钍、射钍、锕。我们也知道有放射性的气体，称为射气。放射性中的物质和效应是多种多样的。总有一片广阔的领域留给实验，我希望在今后的年月里，我们能取得一些美好的进展。我恳切地希望，你们当中有人能把这项科学工作继续下去，并以作出对科学的永久贡献为志向。