46. DIRECT EXTRACTION WITH ETHER. 37 



and the substances thus dissolved estimated. In the majority of 

 cases the weight will be the same as the sum of the substances 

 extracted by petroleum spirit according to 9, and ether according 

 to 36. If there is a deficiency, the residue should be treated 

 with petroleum spirit, in which case attention would be directed 

 to a substance other than an ethereal or fixed oil. The residue 

 after exhaustion with ether, and, if necessary, petroleum spirit, 

 may be dried and boiled with chloroform or bisulphide of carbon, 

 to ascertain if such substances as caoutchouc, etc. can be extracted 

 ( 127). 



