242 EXTRACTS. [CH. IX 



Preparation of extracts. 

 Non-nitrogenous plastic substances. 



For non-nitrogenous plastic substances a given portion 

 of the original material should be treated with successive 

 solvents in the following order : (1) ether or benzene, 

 (2) alcohol of '85 specific gravity, (3) cold water, 

 (4) dilute acid. 



In each case the extraction must be continued till a 

 fresh portion of the solvent fails to extract anything more. 



10 grs. of material and about 250 c.c. of solvent will 

 generally be found convenient quantities. 



I. Extract the dry substance with boiling ether, 

 benzene, or petroleum ether (with boiling point not 

 above 75° C). 



Extract (No. I.) contains oils and fats, ethereal salts of 

 organic acids (esters), resins, terpenes, chlorophyll and 

 colouring matters, etc. 



This extraction is best performed with Soxhlet's appa- 

 ratus for fat-extraction. 



The material in the inner tube is weighed before and 

 after the experiment, dried at the same temperature in 

 each case. 



When the extraction is complete, the inner tube may 

 be placed in a steam-oven to dry the residue before 

 weighing. 



II. Extract the dry residue from I. with boiling 

 alcohol '85 specific gravity (about 55 p.c). 



Extract (No. II.) contains tannins, glucosides, and 

 part of the sugars, etc. 



