PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 557 



It occurred to him that the facility with which that body is eli- 

 minated from its hydrogen and metallic compounds by chromic 

 acid {el-diromoC) would make the latter substance a valuable 

 means of l)ringing about the starch reaction. Experiments com- 

 pletely confirmed this view. For example, a solution of iodide of 

 potassium {jwtamcul), so dik)te that the addition of nitric acid or 

 starch produces no perceptible effect by the further addition of a 

 single drop of dilute solution of bichromate of potash {^potem-chre- 

 meit) will instantly bring about reaction. Such reaction is still 

 more marked when hydrochloric acid {tkalad) was substituted for 

 nitric acid {tJicdanit). Solutions containing one 400,000th of 

 j)otamed gives the iodine reaction at ordinary temperature. 



Cold Bleaching Process. 



M. Tessie du Mothay and M. Kousseau describe very satisfactory 

 trials which they have made of a cold bleaching process, by which 

 all textile matei'ials (whether silk, cotton, linen, flax, wool or any 

 woolly fibre) can be bleached. The agent employed is permanga- 

 nate of soda, slightly acid, prepared by a new and economical 

 process. AVith this salt, the extraordinary properties of which 

 have of late years been much studied, a bath is prepared, in which 

 the materials to be bleached are dipped. They are stirred about 

 with a glass rod from time to time, and after about ten minutes 

 they are taken out of the bath, strongly colored of a violet brown 

 hue by an abundant deposit of oxide of manganese. They are 

 then dipped as quickly as possible in a bath of water, acidulated 

 with sulphurous acid, and again stirred and turned over with a 

 glass rod, and after two or three minutes the materials or thread, 

 originally of a yellow or gra}^ color, are already white. These 

 operations are repeated twice more, ancl the result is a brilliant 

 white, while the fibres are in no way injured. The materials 

 operated upon were cotton fabrics, dirty, as they came direct from 

 the loom, as well as skeins of linen thread, of a dark slate color, 

 which, by existing processes, would have taken many days to 

 bleach. 



Chloride of Zinc as a Disinfectant. 



As the season of vile odors and foul miasms is opening upon us, 

 with a dark cloud of cholora glooming in the horizon, the question 

 of disinfectants assumes more than ordinary interest. We notice 

 in the daily papers a circular from Dr. S. C. Blake, the city ph 

 siciau, recommending the use of chloride of zinc for the purifica- 



