402 Mr. George on th6 [June 



Ninety-five grains of lac dye wei-e boiled three hours in four 

 measured ounces of water, 10 grains of extractive were dissolved, 

 the remaining 85 grains were digested in solution of subcarbo- 

 iiate of soda, and the solution filtered ; on the addition of sul- 

 phuric acid a precipitate fell down, which, when dried, weighed 

 38 grains. It was sparingly soluble in boiling water, and preci- 

 pitated as the water cooled. 



The solution in boihng water had a full peach colour ; sulphu- 

 ric acid first reddened, and then converted it to an orange, 

 muriatic acid very much reddened, nitric acid did not redden so 

 much as the muriatic, supertartrate of potash reddened but not 

 in so high a degree, the acids did not occasion any precipitate, 

 subcarbonate and subborate of soda changed the colour of the 

 solution to a crimson, sulphate of alumina and potash threw down 

 a beautiful dark-crimson precipitate, muriate of tin a bright-red 

 precipitate, sulphate of copper a dull-crimson precipitate, sul- 

 phate of iron a dirty-red precipitate. 



The colouring matter of lac appears to differ from that of 

 cochineal in its sparing solubility in water ; but in the combina- 

 tions tljey both form with the metallic oxides and alumina, they 

 closely resemble each other. 



Its combinations with the metallic oxides, and the permanency 

 of the colours thus formed, bear a striking analogy to those of 

 extractive ; from which it differs in not being precipitated, but 

 rather rendered more soluble by acids, and in its comparative 

 insolubility in water. 



Before entering upon the process for dyeing scarlet with lac, we 

 will examine the other substances employed. On the introduction 

 of lac lake, it was found that the resin with which the colouring 

 matter is combined required the action of a powerful acid for its 

 solution ; for this purpose, sulphuric acid, or a mixture of the 

 sulphuric and muriatic acids, was employed. The use of so 

 great an excess of sulphuric acid is injurious, not only in impair- 

 ing the brilliancy of the colour and converting it to a shade too 

 much approaching to orange, but also in rendering the cloths when 

 dyed harsh to the feel ; indeed these effects prevented its apph- 

 cation except to the coarsest quality of goods. Since the intro- 

 duction of lac dye, muriatic acid alone has been employed, and 

 it has been found quite sufficient to combine with the alumina, 

 and to dissolve any small portion of resin. 



The acid employed is known by dyers as lac spirit, and is 

 formed by dissolving in 60 lbs. of muriatic acid, specific gravity 

 1-190, 3 lbs. of tin ; the solution is colourless and fuming. The 

 solution of tin used scarcely differs from that employed in the 

 dyeing of scarlet with cochineal, except that it contains a larger 

 proportion of oxide of tin. 



The aquafortis (nitric acid) should be distilled in glass vessels, 

 and perfectly free from nitrous gas. The aquafortis most 



