(36 PHILOSOPHICAL TRANSACTIONS. [aNNO IJQI. 



who are situated near places where the lac is plentifully found, to try to extract 

 and preserve the colouring principles by such means as would prevent them from 

 being injured by keeping. I doubt not but in time a method may be discovered 

 to render this colouring matter as valuable as cochineal. 



Mr. Hellot's process for extracting the colouring matter from dry lac deserves 

 to be tried with the fresh lac in the month of Oct. or beginning of Nov. before 

 the insects have acquired life ; for I found the deepest and best colour was pro- 

 cured from the eggs while mixed with their nidus. His process is as follows : 

 Let some powdered gum lac be digested 2 hours in a decoction of comfrey root, 

 by which a fine crimson colour is given to the water, and the gum is rendered 

 pale or straw coloured. To this tincture, poured off clear, let a solution of 

 alum be added ; and when the colouring matter has subsided, let it be separated 

 from the clear liquor and dried ; it will weigh about -|- of the quantity of lac em- 

 ployed. This dried fecula is to be dissolved or diffused in warm water ; and 

 some solution of tin is to be added to it, by which it acquires a vivid scarlet 

 colour. This liquor is to be added to a solution of tartar in boiling water ; and 

 thus the dye is prepared. 



In India, comfrey roots are not to be had ; but any other mucilaginous root, 

 gum, or bark, would probably answer equally well. On some parts on the 

 Coroniandel coast, if not over it all, a decoction of the seeds of a very common 

 plant, cassia tora of Linnaeus, which is exceedingly mucilaginous, is used by the 

 dyers of cotton cloth blue, to help to prepare the blue vat. It suspends the in- 

 digo till a fermentation takes place to dissolve it, and also helps to bring about 

 that fermentation earlier than it otherwise would. The gum lac, or rather 

 resin, itself, is known to be perfectly soluble in spirits of wine. The empty 

 husks which covered the pupa are also soluble in spirits, but without a very large 

 proportion of the spirits is used, it soon becomes thick, like a jelly. Four 

 grains communicated that quality to 3 drams of rectified spirits of wine. This 

 jelly is very difficult of solution in spirits ; a month has not effected it in a heat 

 of from 80 to 90° of Fahrenheit's scale. The substance of which these husks 

 are composed, is an exudation from the larvae themselves, which becomes hard 

 by exposure to the air. The cells seem to be made of a very different substance ; 

 what that is, and the manner in which they are made, remains still to be 

 discovered. 



Explanation of the Figures. — PL 1. 1. A piece of lac on a small branch of mimosa cinerea, natu- 

 ral size. 2. The outside of the top of a cell, with its 3 openings ; the white one with the hairs is 

 still unopened. 3. One of the utriculi for the male flies, with its 2 necks, which correspond with 

 the 2 upper apertures in fig. 2. 4. One of the eggs found in the utriculus, fig. 3, which produces 

 the male flics. 5. The male fly in its perfect state. 6. Small compressed dry grains, found in tlie 

 cellulae with the male flies. The last 5 figures are all much magnified. 7. A small bit of a branch 

 of mimosa cinerea, witli the female insects in their pupa state, natural size. 8. One of the eo-gs 



