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between the oxides of iron of the south and those of the north. The cinnabar of Japan has the same proportions as that of Almaden. Silver is neither oxidated nor muriated differently in the muriate of Peru from the muriate of Siberia. In no part of the known world will you see two muriates of soda, two muriates of ammonia, two saltpetres, two sulphates of lime or of potash, soda, magnesia, or baryta, which are different; in fine, it is with one measure that all the combinations of the globe have been formed."

Page 370. "Nature has imposed certain laws of proportion in relation to those unions which we have come to call combinations."

Vol. lxiii., page 439.

"None of the researches which have been undertaken hitherto to assist the hypothesis of variable oxidations, even among the class of nonmetallic combustibles, have been able to discover above one or two of each; and each of these once oxidized is equally a product, the characters of which are invariable, preserving its properties with firmness on all occasions where they can be shown, whether free or in a state of combination. To this height are we now arrived in this branch of natural science."

Page 466. "There is nothing whatever in opposition to our extension of the same principles by regarding the solutions of sulphur, phosphorus, carbon, arsenic, zinc, &c., in hydrogen, not as simple solutions, without measure, in unfixed proportions, but as proportional combinations, as hydrurets of sulphur, phosphorus, &c., which the excess of the solvent may take into solution."

"Sur les Sulfures Métalliques."

Jour. de Ph., vol. lix., page 261, year 1804.

The following is a portion of the controversy between Berthollet and Proust. It begins with quotations from Berthollet.

"He (Proust) believes that there is attached to antimony

a dose of sulphur invariably fixed by nature, and that it is not in the power of man to increase or diminish it. He fixes this at 25 per cent."

Proust continues, "It is not I, but nature, or whatever power you choose, which places a barrier between it and all the efforts of every chemist who will attempt to make sulphuret of antimony above or below this proportion. I have assigned no law to my discovery; I have verified it only; I have followed the precept which Berthollet himself has traced in his profound work; when, says he, one substance combines with another, it is necessary to determine the proportions, and to examine the properties, &c. Such, in fact, has been the constant object of chemists, from the moment that they recognised that this determination was one of the most important bases of the history of combinations and of the science of analysis. Nobody can believe that nature will abandon her compounds to the chance of those variable proportions which Berthollet has chosen as the foundation of his system. But it is not the less true, that in proportion as the horizon of sulphurets extends, we do not see that the new facts which every day accumulates are of a nature to strengthen it."

Berthollet against Proust. "He has combined the oxide of antimony with different proportions of sulphur, and has obtained mixtures which may be represented by this formula; oxide +1+2+3, &c., of the sulphuret of antimony: has he not obtained there veritable combinations?" Page 262.

Proust: "To this, I shall reply, that solutions which have commenced, or which have not attained the term of saturation of which we consider them capable, ought to be viewed differently from combinations which are completed; but to explain myself, I illustrated those solutions in the same way I would do those of sugar in water, that is, as water+1+2+3 of sugar. I do not see that we can form more distinct ideas of the solutions of the sulphuret of antimony in its oxide. All chemists have hitherto believed that these glasses, livers, and crocuses,

were oxides which had been sulphuretted. The object of my work has been to show the fallacy of this, and that we must give up these sulphuretted oxides, which we admit, without proof, and receive in their place a species of combination, new, without doubt, but well demonstrated. Certainly this combination is in opposition to the ideas of Berthollet; he wishes to place them in the family of sulphuretted oxides, but it is no less certain, that those which I have announced do exist, and that they have this advantage over sulphuretted oxides, the existence of which is now terminated, that they afford the most natural solution of those thousand and one problems in antimony, the ridiculous nomenclature of which has shown the confusion of our ideas, and covered with obscurity the history of that metal."

Page 264. "To a tb. of potash you add an ounce of arsenic; it is not saturated, you add two, you add three, it is not yet saturated, and so with more; but in waiting to discover the point of saturation, I repeat to them; your arsenical potashes are nothing at present but potash, plus one, two, or three of arsenic, but we have not time to prove that this combination will obey, as it no doubt will, the law of proportion, and shall not press you to decide on it. These are results so variable that they destroy your laws of proportions, and render your apothegms illusory. Berthollet is too just not to agree that the series of numbers by which I have sought to represent the solutions of the sulphuret of antimony in its oxide, has not the least relation to that which I have hitherto called portion in combinations."

Journal de Physique, 1805, vol. lix., page 321. "Sur les Oxidations Métalliques."

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"I ought to explain, says Berthollet, that the proportions of oxygen may vary progressively after the limit or the combination becomes possible, until it attains the last degree; and when this does not take place, it is because the conditions

which I have indicated become an obstacle to this progressive action."

"A little before this are to be found the facts on which this illustrious chemist establishes the theory of progressive oxidations, which he opposes to that which I have given out on different occasions, and of which the base is, that the combustible bodies are arrested at fixed terms of oxidation, in the same way as we see to be the case with sulphur, phosphorus, carbon, azote, and the greater part of the metals."

Page 328. After shewing that the fine lead powder got by shaking the metal in a bottle is a mixture of metal and oxide of lead, and not a low and varying degree of oxidation, he adds;

"But is each of these molecules, one might say, suddenly at one leap elevated from 0 to 9, to 12, to 25 per cent? And is it possible that they do not pass successively all the ascending terms which the imagination can conceive possible between the two extremes! I reply, that it is impossible in the actual state of things to say if the oxidation follows or does not follow this progression, because in the calcination of a metal, of lead for example, the senses are not struck with any phenomenon which can guide the judgment in the choice between two opinions; but although we do not see intuitively that which occurs actually in calcination, we are not hindered from judging clearly by the aid of numerous analogies which the field of combination offers."

Page 330. "Let us mix the green sulphate of iron with the red, each base will hold its own amount of oxygen, and there will be no conciliation between the two, no division which will bring forward to us those intermediate oxidations which the mind would desire to discover. Is it a piece of iron which we throw into the red sulphate? We see the base of the salt descend to 28, not by a retrograde march which arrests each of these particles at 47, at 46, at 45, &c. of oxidation, but by the instantaneous lowering of each from the limit (or term),

48 to 28, and this is well confirmed by analysis, because we discover in the solution nothing but red molecules mixed with green ones."

Page 334. "I will say then of the sulphurets as I said of the oxides, there are only two of them."

Speaking of the oxide of copper:

Page 351. "If we establish the calculation on this basis, we find that a quintal of yellow oxide is composed of 86 of copper and 14 of oxygen, whilst the black oxide to which we wish to compare it, contains only 80 of metal and 20 of oxygen; or in other words, if copper condenses 25 per cent. of oxygen to raise it to its maximum, it condenses only 16.3 to raise it to its minimum. Here then, we find, as in all other combinations of oxygen, new reasons for recognising this law of nature, which subjects the metals and combustibles to those proportions from which we cannot separate them, however various may be the circumstances under which they have united."

It really is a melancholy thing to read these papers of Proust. He had advanced by the most careful steps to the conclusion, that all combinations were made in proportions defined by some law of nature, that they were weighed and measured before they were united, and yet failed to see a -law. Richter used the words from the Septuagint, God has made all things by measure, number, and weight; and Proust uses a similar phrase with his "pondere et mensura," from the Vulgate, leaving out the word number, which he did not sufficiently see. He saw, with great clearness, that without such constant proportion the products of nature would lose their stability, and the characters of bodies could not be depended on for permanence. We have here no difficulty in judging how much he did, and how much he left undone; how far his own mind was advanced, and how it had merely speculated. He tells us all distinctly. When he uses +1+2+3 of proportions, he tells us it is merely for illustration, he did not

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