108 



CHEMISTRY. 



was done by fusing the arseniates with excess 

 of chloride of the same base; the arseniates 

 dissolve, forming chlorarseniates, which crystal- 

 lize in the fused mass when it begins to solidify. 

 As in the case of apatite and Wagnerite, fluorine 

 can either wholly or partially replace chlorine 

 without any alteration in the general form. 

 Frerny has described (Comptes Rendus, vol. 

 Ixiii., p. 714) a general method of obtaining, in 

 the form of crystals, many substances which 

 are usually amorphous. It consists in allowing 

 the precipitations and decompositions to take 

 place very slowly. In one series of experi- 

 ments, the substances were dissolved in solu- 

 tions of different densities, containing gum, 

 sugar, gelatine, etc., and these separated by 

 porous substances, or by unsized papers, which 

 were only gradually penetrated by the liquids 

 and thus caused slow decomposition. In other 

 cases, endosmose was resorted to, and the solu- 

 tions were separated by membranes. Vessels 

 of wood or of unbaked porous porcelain, which 

 allowed the substances to pass through very 

 slowly, also gave excellent results. The author 

 obtained by this method, and in very beautiful 

 forms, the sulphates of barium, strontium, and 

 lead, carbonates of barium and lead, oxalate of 

 calcium, borate and chromate of barium, and 

 the various sulphides. In the hope of obtain- 

 ing crystals of quartz, solutions of alkaline sili- 

 cates in porous vessels were placed in dilute 

 acids, and also exposed to the action of carbonic 

 acids. Silicates, under these circumstances, do 

 not deposit gelatinous precipitates, but white 

 crystalline masses hard enough to scratch glass. 

 These were not quartz, however, for they were 

 soluble in alkalies, and contained water and a 

 small quantity of soda, which seems essential 

 to their composition. The crystals from silicate 

 of soda contained 68 silica, 5 soda, and 27 of 

 water in 100 parts. Neglecting the small quan- 

 tity of soda, the composition corresponds to the 

 formula S^+uHO. The author's experiments 

 furnish an elegant confirmation of Chevreul's 

 view of the formation of crystallized oxalate of 

 calcium in the cells of plants, for he succeeded 

 in obtaining crystals of this kind when he al- 

 lowed a soluble calcium salt to act through a 

 membrane on a soluble oxalate. (Phil. Mag., 

 September.) 



At the October meeting of the Eoyal Micro- 

 scopical Society, Dr. Guy read a paper on crys- 

 tallizations and arborescent forms obtained by 

 subliming minute quantities of strychnine and 

 other alkaloids in the manner originally pro- 

 posed by Helwig. Dr. Guy's process is to place 

 the matter to be sublimed at the bottom of a 

 small, flat, porcelain vessel, such as a crucible 

 cover. Over this he puts a square of glass, 

 about one-eighth of an inch thick, with a round 

 hole in the middle ; and over the hole a flat 

 piece of glass. A moderate heat carefully ap- 

 plied by a spirit-lamp sublimes the alkaloid, 

 and it is condensed on the flat plate of glass, 

 and ready for microscopic examination. Quan- 

 tities such as the 10,000th part of a grain give 



satisfactory results. Many photographs of crys- 

 tallizations, exhibited by Dr. Guy, were of great 

 beauty. It was suggested that evidence of this 

 kind might be important in legal inquiries, as 

 forming part in a chain of proof. 



Crystallized Substances from the Brain. In 

 Liebig's Annalen, vol. Ixxxiv., p. 29, is given an 

 account of new substances obtained from an al- 

 coholic extract of brain, by Liebreich, which he 

 csulh protagon. It separates in microscopic crys- 

 tals. Liebreich regards it as a primary constitu- 

 ent of the brain, and widely distributed in the 

 organism. When protagon is boiled for some 

 time with baryta-water, it is resolved into gly- 

 cerine, phosphoric acid, several fatty acids, and 

 anew basic substance, neurine, which forms with 

 bichloride of platinum a double salt, crystalliz- 

 ing from water in hexagonal plates. This sub- 

 stance has been thoroughly investigated by 

 Baeyer, who has shown it to be probable that 

 crude neurine is a mixture of two bases, whose 

 platinum double salts have respectively the for- 

 mulas, N0 6 H M 01, PtCL, and N0 6 H 12 C1, PtCl,. 

 It is thought that choline in the gall, and sinka- 

 line, which is at present found in white mus- 

 tard, are identical with neurine, which thus 

 appears to play an important and varied part 

 in the organic kingdom. 



The Specific. Gravity of Vapors and Gases. 

 Bunsen has recently determined the specific 

 gravity of some vapors and gases by a series 

 of elegant experiments. Six trials for carbonic 

 acid gave the following values : 



1st 1.525 



2d 1.525 



3d.. ...1.528 



4th 1.529 



5th 1.528 



6th... ..1.529 



According to Eegnault's classical researches, 

 the specific gravity of this gas was 1.52901. 

 The specific gravity of the vapor of water was 

 found by Bunsen, in two experiments, to be: 

 1st, 0.629 ; 2d, 0.622. 



Aniline Colors. The display of aniline colors 

 has been pronounced by several authorities one 

 of the most brilliant successes in the chemical 

 department of the Paris Exposition. The spe- 

 cial correspondent of the Chemical News speaks 

 particularly of the methylaniline and dimethyl- 

 aniline violets exhibited under the name of 

 " Paris violet." They are produced by Dr. 

 Hofmann's method, in which the very volatile 

 iodide of methyl is used as a reducing agent, 

 and this would have entailed a considerable 

 loss, if 800 worth a diiy were constantly 

 risked, that being the value of the quantity ne- 

 cessary to produce the one hundred and fifty 

 kilogrammes of methylaniline which the manu- 

 facturers, MM. Poirrier and Chappart, send to 

 market every day. In order to arrive at a re- 

 munerative product, they have substituted a 

 cheaper substance, nitrate of methyl, for the 

 iodide, and it was by that agent that they were 

 able to produce their first ton of " Paris violet " 

 at their chemical works. This mode of fabri- 

 cation was, however, fraught with danger ; and, 

 fortunately, M. Berthelot was able to point out 

 a process less dangerous and cheaper, the treat- 



