CHEMISTRY. 



95 



acid used in the preparation of aniline black 

 should be from iron, or the color has a gray 

 tint. 



The Mechanics* Magazine speaks very highly 

 of Nicholson blue lor wool-dyeing. It differs' 

 from all the other aniline colors in the fact 

 that it is not, like magenta, aniline violet, etc., 

 the soluble salt of a base insoluble in water, 

 but is a base soluble in water of itself, yet 

 capable of forming, in union with acids, col- 

 ors and insoluble salts. The base is in itself 

 colorless and very pale. To obtain a dye, the 

 base already fixed on a fibre must be united 

 with an acid. This is effected by passing the 

 dyed wool through an acid-bath. Thus, for ten 

 pounds of wool, a very dilute solution is pre- 

 pared by boiling one to one and a half ounce 

 of the d'ye in pure water; a color-bath is next 

 prepared, at a hand-heat, in which one and a 

 half to two ounces of borax must be dissolved. 

 An equivalent quantity of the carbonate of 

 potash or soda may be used instead. The borax 

 serves to neutralize any traces of acid existing 

 in the water or the wool to be dyed (possibly 

 also to prevent the working on of certain im- 

 parities which may be present in the dye). 

 The solution of Nicholson blue, previously 

 well filtered, is next added. The goods, pre- 

 viously saturated with water, are next entered 

 and kept constantly in motion, while the tem- 

 perature of the bath is very gradually raised 

 to the boiling-point. They are then taken out, 

 worked well in water at a hand-heat, and 

 passed into the acid-bath, which for ten pounds 

 of wool should contain ten ounces of sulphuric 

 acid. Here they are worked till the color is 

 fully developed. 



The beautiful red-coloring matter called 

 saffranine is to a great extent superseding 

 catharinine for dyeing silk and cotton. To 

 prepare it, heat in a suitable vessel a mixture 

 of two parts nitrite of aniline and one part 

 arsenic acid, for five minutes, to a temperature 

 of 80 to 120 Cent. The contents of the vessel 

 are then thrown into boiling water and neu- 

 tralized with chalk. The liquid takes a pure, 

 beautiful red. It is allowed to settle, and 

 passed through a woollen filter. It is then 

 precipitated with common salt, which is dis- 

 solved in the solution to the extent of five 

 times the weight of the nitrate of aniline em- 

 ployed. After some time the saffranine pre- 

 cipitates, and is collected on a filter, allowed 

 to drain, and pressed, when it is ready for use 

 or sale. Nitrite of aniline is easily obtained 

 by passing a current of nitrous acid through a 

 solution of aniline. Starch and nitric acid are 

 heated in a retort, when nitrous acid is given 

 off. This acid, sufficiently washed, is intro- 

 duced into a mixture of aniline, water, and 

 common salt. The complete conversion of the 

 aniline is indicated by the clear, light-brown 

 color passing into a deep chestnut. It is re- 

 peatedly washed in water, and then used. 



Platinum-Black. The usual methods of ob- 

 taining platinum-black are attended with much 



trouble. Prof. J. Lawrence Smith informs the 

 American Chemist of a new process of making 

 the article. He first reduces the platin-chlo- 

 rides of the alkaline by hydrogen in common 

 street- gas. Then the mass is treated with 

 water to wash out the chlorides of the alkalies 

 thoroughly ; the residue is dried at a tempera- 

 ture not exceeding 220 F., when it is ready 

 for use. The operation can be readily con- 

 ducted in a capsule of porcelain or platinum; 

 the platin-chloride is introduced, and covered 

 with a circular piece of mica a little smaller 

 than the wide diameter of the capsule, with a 

 hole in the centre, through which the tube 

 conducting the gas is introduced. The capsule 

 is then heated by any convenient arrangement 

 by which a temperature not exceeding 400 or 

 500 F. is obtained, at which temperature it 

 can be maintained with a little management ; 

 a small Bunsen burner with a rosette can be 

 used. If the temperature be too high the 

 platinum -black will not be as good as that 

 made at a lower temperature. Washing the 

 platinum-black, after the chloride is taken out, 

 with a solution of caustic potash or soda, and 

 subsequently washing with distilled water, 

 may improve the product. 



Commercial Chloral. Edward E. Squibb, 

 M. D., a manufacturing chemist of Brooklyn, 

 N. Y., sends a valuable paper to the Chemical 

 News, containing his practical observations 

 upon the new and powerful agent, chloral. 

 He finds that the finest specimens of chloral 

 crystallize between 118.4 F. and 123.8 F. ; 

 those which crystallize at the higher tempera- 

 ture having the most anhydrous chloral, and 

 those which crystallize at the lower tempera- 

 ture having an excess of water. Accurately 

 hydrated chloral crystallizes at about 118.4 

 F. to 120.2 F. The large crystals contain the 

 most watery liquid in their solutions, nnd there- 

 fore soonest deliquesce. They keep best in an 

 imperfectly-stoppered, wide-mouthed bottle. 

 Small granular crystals which form from the 

 melted chloral, when carefully under-hydrated, 

 are the best form for convenient practical use. 

 An important test of quality for commercial 

 chloral is its boiling-point. Chloral should not 

 begin to boil fairly below 203 F. ; if it does, 

 it is too much under-hydrated, and therefore 

 too liable to decomposition ; and it should boil 

 down to one-half steadily at 206.6 to 208.4 

 F. If it boils off above the latter point, the 

 indication is that it is over-hydrated and deli- 

 quescent. In conclusion, Dr. Squibb remarks 

 that, while several of the grades of chloral now 

 to be found in the market are worthy of con- 

 fidence, they are by no means uniform, but are 

 improving in this respect. The enormous 

 scale upon which it has been made in Ger- 

 many, and the difficulty of reducing this 

 scale to meet the reaction which fatal cases 

 of poisoning in popular use have caused, have 

 overstocked and very much depressed the 

 market ; and it is to be feared that some of 

 this overstock may become decomposed before 



