596 PHILOSOPHICAL TRANSACTIONS. [aNNO 1775. 



insoluble in water. Oil of vitriol put to it becomes of a red orange colour ; but, 

 when the acid is drained off, the residuum appears purple. Annotto, treated in 

 the same manner, gives a blue colour. Spirit of wine, aether, fixed and volatile 

 alkalies, as also soap, dissolve the colouring part of this substance. To deter- 

 mine the quantity of colouring matter which it contains, 2 drs. were digested in 

 a mattrass, with 4 oz. of rectified spirit of wine; the solution, being filtered, 

 assumed a rich deep yellow colour, like a strong solution of saffron or gamboge 

 with the same spirit ; what remained in the filter was digested a 2d time, with 

 4 oz. of fresh spirit of wine, and the liquor filtered ; this solution was much 

 weaker than the first. The undissolved part remaining in the filter after this 2d 

 solution was digested, a 3d time, with 4 oz. of fresh spirit; but the solution 

 was now quite weak, and of a very pale yellow colour. The residuum being 

 now deprived of its colouring portion, was slowly dried, when it appeared of a 

 very pale yellow colour, felt as soft as starch between the fingers, and weighed 

 42 grs. ; so that f nearly of this colouring substance are soluble in spirit 

 of wine ; the undissolved part is not soluble in water, acids, or alkalies. 

 Put on a red hot iron, it smokes and catches fire without melting, leaving 

 a caput mortuum, and gives a smell similar to that arising from common 

 vegetable matter. The first solution in spirit of wine, after standing 24 hours, 

 deposits some of its colour in the form of minute spiculine crystals, of an orange 

 colour. The 2d and 3d solutions let fall none of their colour. The 1 st solution, 

 dropped on paper, tinges it of a bright orange colour, the 2d gives a lively yellow 

 colour, and the 3d a pale yellow. The 1st solution, sufficiently diluted with 

 spirit of wine, makes a bright yellow stain on paper, no way inclining to an 

 orange, but exactly resembling that made by the 2d solution ; hence it seems 

 probable, that an orange colour is only a deep yellow. Vitriolic aether readily 

 dissolves the colouring part of this substance, and affbrds solutions of nearly the 

 same colour as those made with spirit of wine. Oil of turpentine dissolves but 

 a small portion of it, and acquires only a pale yellow colour. A solution of fixed 

 alkali in water, digested with this substance, dissolves a large portion of its colour- 

 ing part, and the solution is of a brownish yellow colour. Volatile spirit of sal 

 ammoniac, seems to dissolve a larger portion of it than the fixed alkali, and the 

 solution is of a reddish orange colour. A solution of soap in water, boiled with 

 this substance, likewise dissolves its colouring part. All the foregoing solutions, 

 except that in oil of turpentine, which was not tried, dye silk, cloth, and linen, 

 of various shades of yellow and orange ; but these colours are discharged, by 

 boiling the dyed substances for some time in soap and water. This colour can 

 therefore be of use only in dying silk and wool, for which purpose we are 

 already furnished with good dyes. Few colours go so far in dying as this new 

 substance, and none dye so speedily, especially when soap and water are used as 

 the solvent ; for a dip or two will dye cloth or silk of a lively yellow colour, 



