90 



CHEMISTRY. 



reduction of sulphuric acid in the plants, it 

 seemed to me of some interest to try whether 

 the sunlight possesses any reducing power 

 upon the oxygen compounds of sulphur outside 

 of vegetable tissues. For this purpose I ex- 

 posed diluted sulphuric acid, solutions of sul- 

 phates, sulphites, and aqueous sulphurous acid, 

 under various conditions, in sealed tubes, to 

 the sunlight of last summer. With sulphurous 

 acid only did I notice any change ; and even 

 the tubes containing this remained clear dur- 

 ing two months, but after that time a change 

 set in which slowly increased, and sulphur 

 was deposited in a finely-divided state. Sul- 

 phurous acid was thus gradually reduced to 

 sulphur, but oxygen was not liberated; an- 

 other part of the acid having been oxidized by 

 it to sulphuric acid. It seems very singular 

 that such a period (two months) was required 

 to initiate this change ; and it would appear 

 that a previous absorption of a great amount 

 of light was necessary to the separation of the 

 first atom of sulphur, which was followed 

 then, however, by more atoms at shorter in- 

 tervals." 



Artificial Gems. M. Gaudin, who has de- 

 voted many years to the production of artificial 

 crystallized gems especially rubies, sapphires, 

 and emeralds has communicated to the French 

 Academy of Sciences some curious observa- 

 tions on the effect of a powerful oxyhydrogen 

 blow-pipe blast. He says that alumina, by it- 

 self, cannot serve for obtaining precious stones, 

 owing to the tendency of this earth to dovit- 

 rify again. It does not become pasty before 

 fusing, but liquefies at once, and is as fluid as 

 water ; and next volatilizes as if it were cam- 

 phor. In order to render alumina viscous, 

 quartz has to be added ; but that impairs the 

 crystallization, and also the hardness. The col- 

 oration of the stones is another difficulty, since 

 the enormously high temperature of the oxyhy- 

 drogen blast acts upon several substances, such 

 as compounds of gold, silver, palladium, and 

 other metals, in a manner quite different from 

 that of a furnace-fire. Copper is a protean 

 substance in this aspect, and, by dexterous 

 manipulations, may be used to produce many 

 tints of color. Curiously enough, manganese 

 and nickel yield, at this high temperature, an 

 orange-yellow coloration; and chromium, ex- 

 posed to the reducing flame, gives a sky-blue, 

 and, in the oxidizing flame, a deep green, which 

 is smoked (enfume), as it were, and has not 

 even a remote resemblance to emerald green. 

 This color can only be obtained by a special 

 and very well-directed oxidizing manipulation 

 from oxide of copper. 



M. Gaudin, in another paper read before the 

 Academy, remarks that it is far more difficult 

 to obtain artificial crystallized gems in cruci- 

 bles than by the use of the oxyhydrogen 

 blow-pipe, and that only by the latter can real- 

 ly hard stones, capable of resisting the file, be 

 made. 



M. Zchweskofski, of Paris, claims to have 



discovered some peculiar silicic and aluminous 

 ethers ; but it is not true, as is reported, that 

 these yield on evaporation precious stones, and 

 certainly not. diamonds. 



Mineral Crystallization ~by Cold. M. Collas 

 has a theory of the crystallization of the dia- 

 mond and other minerals by cold, which he 

 explains in a note to Les Mondes. His theory 

 is as yet confirmed only by the crystallization 

 of tribasic phosphates of lime, which, he says, 

 is an accomplished fact. The following is a 

 summing up of his paper: The hydrate of 

 the basic phosphate of lime becomes horny 

 by desiccation, pulverulent on being boiled, 

 and crystallizes by congelation. The pre- 

 cious stones, which contain cavities filled 

 with a liquid, are crystallized hydrates, and 

 the liquid alluded to is a remnant of the wa- 

 ter of the hydrate. A hydrate crystallizes 

 in a manner different from that of the crystal- 

 lization of a saturated saline solution. The 

 crystallization of a hydrate by cold (freezing) 

 is a dissociation ; the hydrated substance pre- 

 cipitates entirely in crystalline state. Lastly, 

 the author states that it is a contradiction, so 

 to say, to try to obtain crystallized carbon 

 (diamond) by means of heat. The author's 

 opinion concerning this crystalline carbon is 

 that, at a very remote period of the existence 

 of our globe, hail-storms of diamonds have ta- 

 ken place. And to the paper a map is added 

 indicating, by means of a curved line, the 

 cercle diamantaire i. e., the area within 

 which diamonds are now to be found. Graph- 

 ite is, according to the author, destroyed dia- 

 mond that is to say, diamond which has lost 

 its crystalline state. 



Chlorine as a Refining Agent. Mr. F. B. 

 Miller, F. G. S., one of the assayers of the Syd- 

 ney Eoyal Mint, has detailed to the Chemical 

 Society the working results of his method of 

 separating gold and silver directly by the 

 agency of chemical gas. He says that at the 

 Sydney Mint 6,820,198 ounces of gold have 

 been received for coinage from the date of its 

 establishment, May, 1855, to December 31, 1868. 

 The average composition of this gold would be 

 about 94 per cent, of gold, 5 per cent, of sil- 

 ver, and - per cent of base metals ; the gross 

 amount of silver contained in the gold would 

 be about 334,190 ounces, so that about 24,750 

 ounces of silver per annum have been lost to 

 the colony for the want of a simple process of 

 refinage. The gold now obtained in Queens- 

 land, as also that now brought from New Zea- 

 land, contains a much larger proportion of sil- 

 ver, so that the present loss to the colony is 

 more nearly 42,000 ounces per year. The ex- 

 perience of the Sydney Mint proves that on the 

 average there is a marked deterioration in the 

 gold proceeding from Victoria, where the fine- 

 ness is 96 per cent., northward through New 

 South Wales, where the average is 93| per 

 cent., to Queensland, average 8VJ per cent. 

 The silver can now be readily separated by 

 passing a stream of chlorine gas into the melt- 



