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LXXIIL Analysis of a vegetable colouring Matter. 

 By M. Vauquelin. 



IVl. Thouin has requested me to make an analysis of a new 

 species of lac, which has been sent him by M. Morenas. 



This substance, M. Morenas says, is found in hives constructed 

 by little insects, at the extremities of different trees, which being 

 entirely covered with them go soon to decay. 



Dr. Roxburgh says he observed some thousands of excessively 

 small animals overrunning this lac, and the branches to which 

 it is attached, the greater number of them issuing from small 

 holes which are in the surface of the hives. These insects run 

 swift enough, but they are so numerous that they press one upon 

 another. 



The matter which forms these hives or cells has the appear- 

 ance of transparent amber ; in each cell there appears a little 

 bag filled with a thickish red liquor similar to a jelly; the other 

 part of the cell contains a white matter. 



The Indians have given the name of lackscha to these cells, 

 because of the innumerable quantity of small insects which they 

 inclose — a lack signifying a hundred thousand. 



This lac has a red purple colour approaching to violet ; it has 

 no taste, but it has a smell of amber similar to that of ants. It 

 is neither soluble in water nor in alcohol ; yet with the aid of 

 heat a very slight violet colour may be drawn from it. 



The acids, and especially the sulphuric and muriatic, mixed in 

 water, dissolve this lac very easily, and convert its colour into a 

 bright red. During the dissolution of this matter in the acids, 

 an effervescence is produced by a small quantity of carbonate of 

 lime which it contains. The lac mav afterwards be precipitated 

 from these acid solutions by means of the alkalies, provided no 

 more than a quantity sufficient for exactly saturating the acid 

 is used. The liquor still preserves after this precipitation aslight 

 reddish colour. 



The alkaline carbonates dissolve still more promptly and 

 easily this colouring matter ; the colour which the solution pre- 

 sents is a beautiful violet. As the alkalies precipitate this mat- 

 ter from the acids, so do the acids precipitate it from the alkalies. 

 Flax, silk, or cotton, plunged into solutions of this lac, either in 

 acids or in alkalies, do not take any colour, unless prepared by 

 suitable mordants. 



I have dyed flax of a very beautiful red approaching to 

 scarlet, by plunging it in an alkaline solution of the lac, after 

 having prepared it with a hot solution of muriate of tin, and by 

 turning it by little and little in a mixture of the muriatic aeid 



with 



