246 ANNUAL OF SCIENTIFIC DISCOVERY. 



between six and seven hundred tons ; of madder, one hundred and 

 fifty tons are used weekly. 



The manufacture of disinfectants has also of late become a regular 

 and constant business in England. At an establishment of Mr. Mc- 

 Dougal, at Oldham, England, a disinfecting powder is prepared in 

 which the properties of carbolic and sulphuric acid are taken advan- 

 tage of. This is used to prevent decomposition in stables, cow-houses, 

 and among accumulations of putrescible matter, and generally for 

 the prevention of decomposition in manures. A liquid is also pre- 

 pared with carbolic acid and lime-water, which is applied for the pur- 

 pose of preventing decomposition in sewers, according to the idea of 

 purifying whole cities by preventing the generation of gases in sewer 

 water or among accumulations of animal refuse. The liquid is also 

 used to prevent the decomposition of animal matter when it cannot 

 at once be made use of, especially in the case of meat brought to the 

 market, or animals that have died in the field. The solution of the 

 powder has also been used to some extent in dissecting-rooms, where 

 it immediately destroys any noxious smell, and at once liberates the 

 fingers of the operator from the peculiarly nauseous odor which so 

 often attaches to them. It has also been found useful in the treat- 

 ment of sores, as ^vell as of dysentery. Mr. McDougal has also ap- 

 plied carbolic acid with great advantage to the destruction of para- 

 sitic insects on sheep and other animals. 



ECONOMICAL USES OF WATER-GLASS (SILICATE OF POTASSA 



OR SODA.) 



Mr. J. M. Ordway, in the September number of Silliman's Journal, 

 1861, furnishes a comprehensive article on the history, preparation, 

 and industrial applications of so-called "water" or " soluble " glass, 

 a silicate of potassa or soda. 



In regard to the adhesiveness of this substance, Mr. Ordway states 

 that it has been called a "mineral glue," but that it differs from 

 glue, and most other cementing substances, in continuing to shrink 

 after it has become apparently dry. A strong silicate of soda solu- 

 tion forms a good colorless cement for glass, porcelain, and stone, but 

 when shut up in such impervious substances it is very slow in becom- 

 ing water-proof, and as it does so, its strength is much impaired. For 

 wood and other porous materials it does not answer, since they allow 

 the access of air, which, by its carbonic acid, decomposes the silicate 

 and destroys its tenacity. I have tried silicate of soda in the labora- 

 tory for pasting labels on glass bottles. It does pretty well, only 

 when it is once on it will never wash off, though the paper itself may 

 be removed by washing. It possesses no advantages over gum or 

 flour paste, with the single exception of not being liable to mould by 

 keeping. 



When liquid water-glass, either by itself or mixed with an inert 

 substance, is thinly spread out on any surface, it dries to a strongly 

 adherent, hard, transparent varnish ; but it still goes on absorbing 

 carbonic acid from the air, and the residual silica, being quite incapa- 

 ble of extension, becomes traversed with an infinity of minute cracks, 

 so that the original smoothness and clearness are greatly diminished. 



