BORAX 41Q 



one half the water of crystalhzation and beconio traiiHfomiod 

 to pyroboric acid (HoB^O;). At a red heat all of the water i« 

 expelled and boric anhydride (B.O3) results, which, even at 

 high temperatures is stable and nonvolatile, and for tliis reason 

 it is able to decompose nearly all of the metallic sulphates, 

 forming when fused with them, metallic borates. 



Fused boric anhydride when cold resembles ordinary glass 

 in transparency, hardness, and brittleness. The chief uses of 

 boric acid are in the manufacture of borax; in making colored 

 glazes for the decoration of iron, steel, and other metallic 

 objects; in enamels and glazes for pottery; in the manufacture 

 of flint glass and strass or paste from which artificial stones 

 are cut; in making Guignet's green; as an antiseptic in medi- 

 cine and surgery; and as a preservative for fish, meat, milk, 

 and other foods. 



The principal methods used in the manufacture of boric 

 acid are thus described: 



In the chlorine or IMoore process which is used to some 

 extent in England, the crude colemanite in powdered form is 

 suspended in water and heated to 70° C. ; then chlorine gas is 

 passed into the liquor and reacts on the colemanite, forming 

 boric acid, calcium chloride and calcium chlorate. The 

 greater part of the boric acid crystallizes out upon cool- 

 ing and is subsequently purified by repeated crystalliza- 

 tions. The residue solution, called mother liquor, is used many 

 times mitil the accumulated calcium salts begin to separate 

 out in the form of crystals. 



The mode of procedure in the hydrochloric acid process is 

 as follows : Two parts by Aveight of hydrochloric acid and four 

 parts of water (the volume of the latter being kept constant) 

 are used, in which the calcium borate is boiled until dissolved. 

 The boric acid is then crystalhzed out of the cooled liquor, 

 leaving the calcium chloride still in solution. Before the 

 crystals are in proper condition for packing and shippiiig, an 

 additional treatment is necessar}-, which consists of draining, 

 whizzmg, and washing with cold water, concluding with a 

 second and final whizzing. In Germany the hydrochloric acid 

 process is used to extract the boric acid from the boracite 

 contained in the famous Stassfurt salt deposits. The material 



