56 UTILIZATION OF MINUTE LIFE. 



for varnishes, japanned ware, and sealing-wax, and 

 sometimes as a substitute for cochineal in dyeing 

 scarlet. Formerly large quantities of lac-lake pre- 

 cipitated from an alkaline solution of the resin by 

 alum, was manufactured in Calcutta and exported 

 to England. At present it is imported from the 

 East Indies in two forms. Shell, stick, and seed- 

 lac (the resinous exudation) arrives in Liverpool at 

 the rate of about two hundred tons per annum. It is 

 principally used for varnish. Lac-dye or cake-lac, 

 and lac-lake (the colouring matter of the insect 

 combined with alumina, etc.) arrives in Liverpool at 

 the rate of about seventy tons per annum. It is 

 used exclusively for dyeing. 



Carminium } the colouring matter of the cochi- 

 neal, is a very interesting substance. It was first 

 extracted from the Coccus cacti by Pelletier and 

 Caventou in 1818. They observed that it formed 

 with alumina a magnificent lake, which they 

 called carmine. This lake was, however, previously 

 formed many years before by Dr. Bancroft. M. 

 Lassaigne discovered carminium in the kerrnes 

 (Coccus ilids), and Chevreul asserted that it existed 

 also in lac-dye (product of the Coccus lacca). It has 

 also been extracted from Coccus polonicus, etc. 



The reason why all these insects cannot be em- 

 ployed so advantageously as Coccus cacti, is simply 

 because they yield a much smaller proportion of 



