BORAX 433 



contain the liquors. When the whole acid has been added, the fire must be damped 

 by being covered up with moist ashes, and the copper must be covered with a tight 

 lid and blankets, to preserve the temperature uniform. The whole is left in this state 

 during 30 hours ; the clear liquor is then drawn off into shallow crystallising vessels 

 of lead, in which it should stand no higher than 10 or 12 inches, to favour its rapid 

 cooling. At the end of three days in winter, and four in summer, the crystallisation 

 is usually finished. The mother-water is drawn off, and employed, instead of simple 

 water, for the purpose of dissolving fresh crystals of soda. The crystals are carefully 

 detached with chisels, re-dissolved in boiling water, adding for each 220 Ibs. of borax, 

 22 Ibs. of carbonate of soda. This solution marks 20 B. (specific gravity 1-160); 

 and, at least, one ton of borax should be dissolved at once, in order to obtain crystals 

 of a marketable size. Whenever this solution has become boiling hot, it must bo run 

 off into large crystallising lead chests of the form of inverted truncated pyramids, 

 furnished with lids, inclosed in wooden frames, and surrounded with mats to confine 

 the heat. For a continuous business there should be at least 18 vessels of this kind, 

 as the solution takes a long time to complete its crystallisation, by cooling to 30 C. 

 (86 F.) The borax crystals are taken out with chisels, after the liquor has been 

 drawn off and the whole has become cold. 



One hundred parts of the purest acid, usually extracted from the lakes of Tuscany, 

 contain only 50 parts of the real boracic acid, and yield no more, at the utmost, than 

 140 or 150 of good borax. 



A considerable saving of expense in manufacturing borax, and a more ready appli- 

 cation of the borax to use, has been proposed by Saulter, as follows : Take about 38 

 parts of pure crystallised boracic acid, pounded and sifted ; mix them well with 45 

 parts of crystals of carbonate of soda, in powder ; expose the mixture upon wooden 

 shelves to heat in a stove-room ; and rake it up from time to time. The boracic acid 

 and the alkali thus get combined, while the carbonic acid and water are expelled ; and 

 a perfect dry borax is obtained. 



Borax is an acid borate or biborate of soda, usually crystallised in oblique prisms, 

 with 10 atoms of water. Under certain conditions it may also be obtained in octa- 

 hedra, containing only half this proportion of water ; and by application of heat the 

 whole of the water may be expelled with intumescence. The composition of these 

 three forms of the salt may be thus exhibited : 



Prismatic Borax (NaO, 2B0 3 , 10HO). 



2 atoms of boracic acid 70 or 36-6 



1 soda 31 16-3 



10 water 90 47'1 



191 100-0 



Octahedral Borax (NaO, 2BO', 5HO). 



2 atoms of boracic acid 70 or 47'9 



1 soda 31 21-2 



5 water . . . . . . 45 30'9 



146 100-0 



Anhydrous Borax (NaO, 2B0 3 ). 



2 atoms of boracic acid . . ^ . . 70 or 69'4 

 1 , N soda 31 30-6 



101 100-0 



Borax has a sweetish, somewhat lixivial taste, and affects vegetable colours like an 

 alkali ; it is soluble in 12 parts of cold, and in 2 parts of boiling water. It effloresces 

 and becomes opaque in a dry atmosphere ; it appears luminous, by friction, in the 

 dark. It melts at a heat a little above that of boiling water, and gives out its water 

 of crystallisation, after which it forms a spongy mass, called calcined borax. The 

 octahedral borax, which is prepared by crystallisation, in a solution of T255 specific 

 gravity, kept up at 145 F., is not efflorescent. When borax is ignited, it fuses into 

 a glassy-looking substance. 



Dry borax acts on the metallic oxides, at a high temperature, in a very remarkable 

 manner, melting and vitrifying them into very beautiful coloured glasses. On this 

 account it is a most useful re-agent for the blowpipe. Oxide of chrome tinges it of an 

 emerald green ; oxide of cobalt, an intense blue ; oxide of copper, a pale green ; oxide 



VOL. I. E F 



