12 



CHEMICAL INVESTIGATION OF LAC. 



The most important chemical investigations of Japanese lac 

 have been made by three Japanese chemists. Ishimatsu 9 made 

 the first chemical investigation. He states that the lac has a 

 sweetish odor, an irritating taste, burns with a luminous flame 

 emitting dense black smoke and mixes with fixed oils in all pro- 

 portions ; hence these oils are frequently used as adulterants. 



He states that it was generally supposed that the hardening 

 was due to the action of light and air, but he proves that light 

 is practically without effect on the lac, as it is blackened very 

 rapidly when exposed to moist atmosphere during the night or 

 when kept in a light-tight box. It is unacted upon even in sun- 

 light when kept under water, or in carbonic acid in a sealed flask. 

 It dries very slowly in dry air. This he attributes to the rapid 

 drying of the surface, which prevents the evaporation of the 

 volatile constituents, while in moist air the drying takes place 

 so slowly that the volatile constituents have time to escape. This 

 theory is not in harmony with the statement which immediately 

 follows, where he states that the hardening in the atmosphere 

 is, in all probability, due to the oxygen of the air. 



He finds that the fresh lac yields 58.24% of substance soluble 

 in alcohol, while the perfectly dry powdered lac yields only 

 18.07% t substance soluble in alcohol. He attributes this differ- 

 ence to the fact that the alcohol has greater difficulty in getting 

 at the dry lac. He fails to realize that the difference is due to 

 a chemical change. 



He reports that the lac consists of a substance soluble in 

 alcohol, a gum soluble in hot or cold water, a residue insoluble 

 in alcohol or water, which consists of bark, cellulose, dust, etc. 

 There is also present a small quantity of volatile poison and water. 



His method of separation was to extract the lac with absolute 

 alcohol, evaporate the alcohol and dry at 100 C. to constant 

 weight. 



The residue insoluble in alcohol was extracted with hot 

 water, filtered and the filtrate evaporated, dried at 100 C. and 

 weighed as gum. 



9 Chemical investigation of Japanese Laquor, or Urushi. Manches- 

 ter Literary and Philosophical Soc. 3 series, 1882, p. 249. Communicated 

 by Professor Roscoe, Read Feb. 18, 1879. 



