374' - THE TINCAL OF ASIA, AND ITS APPLICATIONS. 



that, when put into starch, it improves the colour, and renders the muslin 

 incombustible ; also instead of soda, for softening the water, and giving 

 increased whiteness to the linen, without injuring the texture of the 

 fabric. It is very useful as a hair-wash, for cleansing the hair, and remov- 

 ing scurf, &c. ; and is an excellent dentifrice, not injimng the enamel of 

 the teeth, and being very clean in its use. It is frequently used in the 

 teapot, to soften the water, and assist in extracting the flavour of the tea ; 

 and when taken in combination with carbonate of soda and tartaric acid, 

 forms a cooling beverage. 



Good borax, refined from tincal, contains in 100 parts, soda 16, boracic 

 acid 40, water 44, being rather less water and more boracic acid than the 

 ordinary borax. 



Borax also enters into the composition of some varieties of glass. A 

 glass suited for optical purposes is made with seven parts of red lead, 

 two parts of calcined borax, and three parts of ground quartz. The 

 addition of a little borax to the materials for plate glass and crown glass 

 has been recommended ; but a large quantity seems to communicate an 

 exfoliating property to the glass. The vitreous body of artificial gems 

 called strass (from the name of its German inventor) is a kind of flint-glass, 

 in most receipts for which borax is mentioned as an essential constituent. 

 According to Dr Shaw ('Chemical Lectures'), by fusing together four parts 

 of borax and one part of fine white sand, a pure glass is formed, sufficiently 

 hard to cut common glass like the diamond. 



Borax is used to a large extent in assaying metallic ores, to dissolve 

 the mineral and facilitate the reduction of the oxide by carbonaceous 

 matters. It is eminently adapted for this purpose, as it forms fusible com- 

 binations, not only with bases, but also with silica. On this property of 

 dissolving metallic oxides is founded the use of borax to braziers, silver- 

 smiths, jewellers, electro-platers, and others, in the soldering of metals ; 

 for which purpose merely, several tons of borax are consumed in Birming- 

 ham and its neighbourhood weekly. An aqueous solution of borax has the 

 remarkable property of dissolving shellac, affording a solution which 

 may be employed as a sort of varnish. The proper proportions of the 

 materials are five parts of borax and one of shellac. — (Parnell's 'Applied 

 Chemistry.') 



Borax is sometimes sophisticated with common salt, and occasionally 

 with alum. The presence of the former is easily detected by adding a few 

 drops of a solution of nitrate of silver, which would afford a white curdy 

 precipitate of chloride of silver, insoluble in nitric acid if the smallest 

 quantity of common salt is present. The presence of alum in the borax 

 may be detected by ammonia, which gives, with that salt, a white frothy 

 precipitate of alumina, but nothing of the kind with borax. The amount 

 of soda in borax may be estimated by observing how much free sulphuric 

 acid must be added to the solution of borax to give it an acid reaction, 

 precisely after the manner of the common alkalimetrical process for 

 determining the value of a specimen of carbonate of soda. 



