M. TECHNOLOGY. 501 



power; and since the bleacliing agent is never entirely re- 

 moved, it may also very easily affect wine injuriously when 

 used for clarifying it, and it may prove even more objection- 

 able for medicinal and culinary purposes, although preferred 

 to the natural isino-lass on account of its color. Besides, 

 only bleached isinglass can be adulterated with gelatin, and 

 recently an impure article of this kind has been largely man- 

 ufactured, which can scarcely be distinguished from the 

 bleached and but slightly opalescent genuine article, Avhile 

 the Astrachan isinglass, even when soiled or dark and bloody, 

 is fully as effective as the bleached. The chief characteristics 

 of the genuine article are its freshness of appearance and pe- 

 culiar opalescence. 5 C, XL., 214. 



BLEACHING SPONGES. 



Sponges are said to be bleached by the following process, 

 without the emission of injurious or unpleasant gases: Tliey 

 are first covered with hydrochloric acid, for the removal of 

 calcareous matter, and, after being washed with water, are 

 immersed for five or ten minutes in a solution of one part of 

 potassium or sodium permanganate to forty-five of w^ater, in 

 which they acquire a dark-brown color, which disappears on 

 immersino; them for one or two minutes in a solution of one 

 part of oxalic acid in fifty parts of water, with the addition 

 of a little sulphuric acid. They are then thoroughly washed 

 with water. The brown color acquired may also be removed 

 without injury by repeated immersions for several minutes 

 in very dilute sulphuric acid. 13 C\ JVove?nber 1, 13G7. 



UTILIZATION OF CHROME-ALUM. 



Although the chrome-alum occurring as a refuse product 

 in the manufacture of certain coal-tar colors is reconverted in 

 some cases, by Strohmeyer's process, into bichromate, in many 

 cases it is entirely disregarded, owing to the tediousness and 

 expensiveness of that method. A new way has recently been 

 devised, which, it is claimed, does not require evaporation of 

 the original refuse liquid, permits the almost complete re- 

 covery of the agent employed, and furnishes a liquid ready 

 for immediate use. The product is said to amount to twenty- 

 three and a half per cent, of the chrome-alum, so that the 

 process may even be found profitable, aside from its use in 



