L. TECHNOLOGY. 433 



tance, and is now prepared, either separately or in its combi- 

 nations, as a regular commercial product. The extensive and 

 increasing use of tungstate of soda for rendering fabrics wa- 

 ter-proof and for other purposes, is well known. Tungstate 

 blue is now taking a high rank as a dye. This is equal in 

 appearance to the finest Prussian blue, resists the action of 

 acids, and may be heated to 350 Fahr. without injury. It 

 has the great advantage over Prussian blue of being unaffect- 

 ed by sunlight, which develops the color, and, after the maxi- 

 mum of intensity has been obtained, renders it indestructible. 

 The color is equally visible in daylight and in artificial light. 

 The process of manufacture proposed consists in successively 

 dissolving in a sufficient quantity of water ten parts of the 

 tungstate of soda, eight parts of the photochloride of tin, five 

 parts of yellow prussiate of potash, and one part of perchlo- 

 ride of iron. When these materials have been added to the 

 mixture and well shaken, the deposit found is removed from 

 the fluid, either by decanting or by filtering, and, when suffi- 

 ciently drained, it is exposed, in thin layers on plates, to the 

 action of the sun for several days. 8 A, April 1, 1870, 68. 



ARSENIOUS ACID AND ALBUMEN. 



The preservation of albumen for manufacturing purposes 

 is a problem of much interest, in view of the great use of this 

 substance in the arts, one method consisting in the addition 

 of a slight amount of arsenious acid, or arsenite of soda. The 

 use of the former is, however, sometimes inconvenient on ac- 

 count of the great insolubility, and that of the latter is occa- 

 sionally objectionable on account of its alkaline action affect- 

 ing the application of the albumen. For the purpose of ob- 

 viating these objections, Paraf suggested the boiling of the 

 arsenious acid with glycerine, in which it is quite soluble; 

 after allowing the solution to cool, and to stand for twenty- 

 four hours, a few drops may be added to the albumen. The 

 same substance can be added to gum arabic, paste, and other 

 substances, to prevent fermentation, putrefaction, and the de- 

 velopment of fungi. It will, of course, be understood that 

 arsenic in this preparation is highly poisonous, and its use 

 with substances intended to be eaten is therefore out of the 

 question. 24 C, xviii., 142. 



T 



