120 



CHEMISTRY. 



the superior qualities; pure cotton-seed oil is 

 turned black ; oil of earth-nuts (Arachis) takes a 

 red-brown color and finally turns green, losing 

 its transparency; oil of sesame takes a deep- 

 red color and remains reddish ; oil of colza takes 

 yellowish-green colors and becomes turbid ; nat- 

 ural butter preserves its natural color; oleo- 

 margarine becomes a brick red, and this may be 

 detected even in samples containing as little as 

 5 per cent, of margarine. 



A discussion in the American Chemical So- 

 ciety at its annual meeting for 1891 resulted in 

 the conclusion that carbonate of ammonia is the 

 best substance of the kind for use in making 

 bread and in baking-powders. Ammonia, it 

 was said, makes the gluten of the flour more 

 soluble, to the consequent improvement of the 

 bread in digestibility. Because of its extreme 

 volatility, the salt is completely expelled from 

 the bread in the process of baking. Experi- 

 ments by Prof. J. W. Mallet show further that 

 the ammonia serves to neutralize any organic 

 or lactic acid present in the flour. 



Vegetable transformations, according to M. 

 Em. Bourquelot, go on in mushrooms even after 

 they are gathered, and may in a few hours affect 

 the disappearance of trehalose and the produc- 

 tion of mannite. The author has therefore taken 

 the precaution of plunging his mushrooms into 

 boiling water immediately after they are gath- 

 ered, so as to arrest all change. 



A manufactory of spurious coffee has been de- 

 tected at Lille, at which were used 15 kilogrammes 

 of chickory, 35 kilogrammes of flour, and 500 

 grammes of iron sulphate the last to imitate 

 the natural color of the grain. Luster was 

 given by means of an oil. 



Miscellaneous. Continuing his investiga- 

 tions of allotropic silver, Mr. M. Carey Lea has 

 found that the gold and copper colored forms on 

 the one hand, and the blue, bluish-green, and 

 steel forms stand in close relations to each other. 

 Both are capable of passing into the yellow in- 

 termediate form indifferent to reagents. Blue 

 silver can also be converted, through the agency 

 of sulphuric acid, into yellow at ordinary tem- 

 peratures, with retention of its active properties. 

 By other experiments the author finds that from 

 a single solution, and using one substance only as 

 a precipitant, the whole range of different forms 

 of allotropic silver can be obtained, by simply 

 varying the proportions of the precipitant. A 

 well-marked tendency of acids is to give rise 

 to the yellow product, and of alkalies to the 

 blue. Both substances can be obtained from 

 neutral solutions, and slight changes are suffi- 

 cient to alter the product. While the presence of 

 an organic substance has been found most usually 

 conducive to the production of the allotropic 

 form, this Is not essential, and the author has ob- 

 tained it, transitorily, with hypophosphorous and 

 phosphorous acids. Light has a reversing effect 

 upon this form of silver, first exalting its sensi- 

 tiveness, and then destroying it. The phenomena 

 connected with the reduction of silver, observed 

 under a variety of conditions, seem to lead up to 

 the conclusion that when the reduction is direct 

 from the condition of the normal salt or oxide 

 to that of the metal the reduced silver always 

 appears in its ordinary form ; but when the re- 

 duction is indirect, when the change is first to 



suboxide or to a corresponding subsalt, the sil- 

 ver presents itself in one of its allotropic states. 

 The facts on which this conclusion is based lead 

 to the question whether silver exists in its sub- 

 salts in the allotropic form. Among the facts 

 that support this view is the rich and varied 

 coloration of the subsalts corresponding to the 

 variety of color of allotropic silver, while the 

 normal salts when formed with colorless acids 

 are mostly colorless. On the other hand, -the 

 greater, activity of allotropic silver and its less 

 specific gravity seem to indicate a simpler molec- 

 ular constitution than that of normal silver. 



To obtain a fuller knowledge of the behavior 

 of palladium toward the electric current, Edgar 

 F. Smith and Harry F. Keller first experimented 

 in the electrolysis of the double cyanide in an 

 excess of potassium cyanide. Metallic deposi- 

 tion did not occur until after the expiration 

 of thirty-six hours, or till the excess of potas- 

 sium cyanide had been converted into alka- 

 line carbonates. The deposition was black, but 

 the precipitation was not at all complete. No 

 deposition of oxide was noticed on the positive 

 pole. With a feeble current acting on a solution 

 of palladious chloride in the presence of a large 

 excess of potassium sulpho-cyanide, the deposi- 

 tion was exceedingly rapid, accompanied with 

 noticeable spongy spots, and black. The next 

 attempt was made with palladamonium chloride, 

 in just sufficient ammonium hydroxide to retain 

 it in solution. The precipitation was incomplete 

 after a night of action, but a deposition at the 

 positive pole, which first gradually increased in 

 mass and assumed a black color, had disappeared ; 

 and in all instances where the ammonium hy- 

 droxide was in decided excess the precipitation 

 of oxide at the positive pole was not observed. 

 The palladium thrown out upon the platinum 

 dish in these experiments being very slow in dis- 

 solving, the platinum dishes were in subsequent 

 experiments first coated with a layer of silver. 

 In these experiments, of which six are described, 

 the precipitations were complete, the differences 

 between the amounts found and the amounts 

 calculated coming within the limit of error, and 

 the deposits were bright, metallic, and dense, 

 without sponginess. 



Continuing his experiments in electrolytic 

 separations, Mr. Smith, assisted by Lee K. 

 Frankel, acting upon the observation made in 

 the palladium experiments that the deposition 

 of that metal from the solution of its double 

 cyanide was not possible so long as any unde- 

 composed potassium cyanide remained in the 

 solution, attempted the separation of the palla- 

 dium from the metals which are deposited from 

 their double cyanide solutions. With solutions 

 of mercuric chloride and palladium chloride 

 plus potassium cyanide, the separation of mercury 

 was satisfactorily effected in sixteen hours. The 

 separation of mercury from arsenic likewise pro- 

 ceeded without difficulty. The separation of 

 cadmium from arsenic. was not complete unless 

 the arsenic existed in the solution as the higher 

 oxide. Similar conditions control the separation 

 of silver from arsenic and of copper from 

 arsenic, but in the latter case a stronger current 

 is necessary. Satisfactory results were obtained 

 in the separation of copper from arsenic in a 

 solution containing an excess of ammonia ; but 



