132 TEXTILE FABRICS. [V. 



tin. The concentrated solution of tin thus obtained is eva- 

 porated in a tin pan, containing an excess of granulated tin ; 

 so that the pan will not be acted on, because it becomes posi- 

 tively, and the granulated tin negatively, electric. All copper 

 present in tke solution is precipitated as a black powder on 

 the granulated tin. 



Salts of Tin. — Bouquet, in his paper upon the preparation 

 of some protosalts of tin (Journ. de Pharm. xi. 460), gives 

 the following formula for making the sulphate of the protoxide 

 (SnO,S03). Dissolve recently precipitated protoxide of tin 

 in warm dilute sulphuric acid. Nacreous plates of sulphate 

 separate on cooling. 



Stannate of Soda. — It is usually made by adding caustic 

 soda-lye to a solution of chloride of tin. Another method, 

 suitable for dyeing and color-printing, consists in heating 221fo 

 caustic soda in an iron crucible to a red-heat, adding 8ft) soda 

 saltpeter and 4ft) common salt, bringing it to fusion, and then 

 adding 10ft) granulated tin. The heat is continued until ig- 

 nition takes place and the mass has a doughy consistence. 

 It may be powdered and used at once, or may be purified by 

 solution in water and crystallization. (Journ. of Arts, 1846.) 



Arseniate and Stannate of Soda. — Stannate of soda is made 

 as usual from oxide of tin and soda, or tin and nitrate of soda, 

 and dissolved in water until it reaches 50° Twaddle, and about 

 l|-ft) arseniate of soda (made by fusing together equal parts 

 of arsenious acid and nitrate of soda) is added to a gallon of 

 the hot solution, in an iron vessel over the fire. As soon as 

 a little of the mass taken out congeals at once, the compound 

 is completed. In like manner, phosphate of soda may be added 

 to the stannate, in order to make phosphate and stannate of 

 soda. (Lond. Journ. Aug. 1850.) 



Lead 3Iordants. — The best mordants of lead are ; 1. Basic 

 acetate of lead, obtained by digesting litharge in a solution 

 of sugar of lead ; 2. Potassa-lime and oxide of lead, obtained 

 by digesting litharge in a solution of caustic potassa contain- 

 ing lime ; and, 3. A similar solution with soda instead of po- 

 tassa. All these mordants give a beautiful chrome-yellow. A 



