14-9 



liquefied by fire, and formed into cakes. And, 4. Shell lac, being the 

 original comb, liquefied in water, strained through a cotton clotH, and 

 spread upon a junk of a plantain-tree so as to form thin transparent 

 lamina? : this kind contains the least of the tinging substance, as may 

 well be expected from the mode in which it is prepared. 



Among the chemists who have hitherto analysed this substance, 

 none deserve notice except M. Geoffrey ; but our author's present 

 labours render his investigations of little or no avail. 



The first section of this paper treats of the effects of different 

 menstrua on the varieties of lac, from which it appears that it is so- 

 luble in alkalies, and in some of the acids. And the second section 

 contains an account of the analytical experiments made on stick, 

 seed, and shell lac. From the ample series of facts herein contained, 

 of which it is in vain to attempt a compendious abstract, we collect 

 in general that the varieties of lac consist of four ingredients, namely, 

 extractive colouring matter, resin, gluten, and a peculiar kind of 

 wax ; and that the resin is the predominant ingredient, insomuch 

 that, strictly speaking, we ought to consider lac as consisting prin- 

 cipally of resin mixed with certain proportions of a particular kind 

 of wax, gluten, and colouring extract. The mean results of the ex- 

 periments give the proportions as follows : 100 parts of stick lac 

 are found to contain resin 68, colouring extract 10, wax 6, gluten 5^, 

 and extraneous matter 6^ ; seed lac, resin 88^, colouring extract 2^, 

 wax 4^, gluten 2 ; and shell lac, resin 90'90, colouring extract \, 

 wax 4, and gluten 2'80. Each of these ingredients, we must ob- 

 serve, has been separately and carefully analysed. 



The third and last section contains a number of general obser- 

 vations, chiefly relating to the uses of this substance. From the 

 whole of the experiments here related, it appears that although lac 

 be indisputably the production of insects, yet it possesses few of the 

 characters of animal substances ; and that the greater part of its ag- 

 gregate properties, as well as those of its component ingredients, are 

 such as more immediately appertain to vegetable bodies. Its uses 

 are various, and some of them important. The Indians manufacture 

 it into rings, beads, and other female ornaments. When formed into 

 sealing-wax, it is employed as a japan, and is likewise manufactured 

 into different coloured varnishes. The colouring part is formed into 

 lakes for painters ; and as a dyeing material it is in very general use. 

 The resinous part is employed to make grindstones, by melting and 

 mixing it with about three parts of sand, or with a like proportion 

 of powder of corundum for those stones which are used by lapidaries. 

 We owe to Mr. Wilkins the information, that a peculiar and ex- 

 cellent kind of ink is prepared by the Hindoos of shell lac, dissolved 

 in water by the mere addition of a little borax, and by adding to the 

 solution a certain quantity of ivory- or lamp-black. This process has 

 the further advantage of teaching us to prepare an aqueous solution 

 of lac, which probably will be found of very extensive utility, espe- 

 cially in the preparation of varnishes and pigments, which, when 

 perfectly dry, will not be easily affected by damp or water. 



