L. TECHNOLOGY. 523 



sulphate of ammonia is furnished by gas-works; Glauber's 

 salts and hyposulphite of soda by soda factories ; while the 

 various salt-works furnish Epsom salts. The action of each 

 is about the same, though, perhaps, the Epsom salts yields the 

 most transparent article. 14 (7, CCL, 367. 



FIRE-PROOF SOLUTION. 



The use of the following solution is recommended as a 

 method of rendering woven fabrics more or less incombusti- 

 ble : Three parts of borax and two and a half of sulphate of 

 magnesia are to be mixed with twenty parts of water just 

 before using, and the fabrics are first to be thoroughly im- 

 pregnated with the solution, then wrung out, and washed 

 after having become nearly dry. The use of a mixture of sul- 

 phate of ammonia and sulphate of lime is also recommended. 



FIRE-PRO OF MATERIAL. 



A recent patent of a material for making fire-proof wearing 

 apparel, paper, wood, etc., lately taken out by Carteron and 

 Rimmel, depends for its principle on the exclusion of oxygen, 

 thereby preventing the spread of the flame ; so that, although 

 the fire may actually consume the material which has become 

 ignited, it can not be propagated or extended. The substance 

 used in this new process consists of equal quantities of chloride 

 of calcium and acetate of lime, which are treated in a partic- 

 ular way, and result in the formation of crystals which con- 

 stitute the substance in question. These crystals are mixed 

 with the paint, color, or varnish for coating wood, and with 

 the starch used in starching fabrics of any kind. For paper, 

 it is mixed with the size of the size-bath, or sprinkled on the 

 sheet or web after the sizing. 18 A, September 15, 1871, 631. 



BEST POWDER FOR POLISHING GLASS. 



According to the London Engineer, the best powder for 

 polishing glass or metals is probably that used by Lord Ross 

 in preparing the mirror of his great telescope. This is pre- 

 pared by extracting the peroxide of iron from a solution of 

 pure sulphate of iron by precipitating it by means of ammo- 

 nia. The deposit is washed, pressed until almost dry, and 

 then brought to a dull red heat, just visible in the dark. The 

 only points of importance are in reference to the purity of the 



