Polytechnic Association Proceedings. 937 



alcohol, then mix it with sweet milk to a proper consistency, when 

 it is ready for use. It dries almost instantaneously, and will not 

 crack or rub off. The same process will apply when, other color- 

 ing substances are substituted for lampblack. 



LUTE FOR THE LABORATORr. 



Chemists experimenting with chlorine gas will find Sorel's oxy- 

 chloride of zinc an excellent lute. It is made by mixing commercial 

 zinc white with half its bulk of fine sand, adding a lye of chloride 

 of zinc of 1.26 specific gravity, and rubbing the whole thoroughly 

 together in a mortar. The mixture must be applied as soon as 

 made, for it hardens very quickly. Any apparatus luted with this 

 material will serve for at least three months. 



NEW YELLOW DTE. 



Martius has obtained from the naphthaline of gas works, diuitro- 

 naphtyl, by treating a solution of muriate of naphtylamin and 

 nitrate of potash with nitric acid. The new compound is a weak 

 acid which is purified by crystalization. It is scarcely soluble in 

 water, but more so in alcohol. Its salts are either orange or 

 minium-red in color. The yellow principle serves for dyeing wool 

 and printing carpets. It yields brilliant golden-3''ellow tints; not 

 greenish ones like those from picric acid. 



ARTIFICIAL GEMS. 



The base of these gems, as patented by the superintendent of 

 the Eoyal Porcelain Works at Berlin, is a flux obtained by melting 

 together six drachms of Ary carbonate of soda, two drachms burnt 

 borax, one drachm saltpeter, three drachms minium, and an ounce 

 and a half of purest white sand. To imitate in color, but of course 

 not in composition, the following minerals, add to the flux the 

 ingredients named in connection with each gem: 



Sapphire, — Two grains carbonate of cobalt. 



Opal. — Ten grains oxyd of cobalt, fifteen grains oxyd of manga- 

 nese, and from twenty to thirty grains protoxyd of iron. 



Amethyst. — Four to five grains carbonate of peroxyd of man- 

 ganese. 



Gold Topaz. — Thirty grains oxyd of uranium. 



Smaragd. — Twenty grains protoxyd of iron, ten grains carbonate 

 of oxyd of copper. 



Beryl. — Ten grains protoxyd of iron. 



