306 



PHYSIOLOGY OF NUTRITION. 



with the fat is so small, that in the quantitative determination of 

 fats in plant structures it is generally unnecessary to notice these 

 impurities. In determinations of fat it is convenient to use the 

 apparatus depicted in Fig. 111. 



The apparatus, constructed as described by Soxhlet, is to be 

 obtained from Muencke, in Berlin, at a price 

 of about 10 m. It consists of the flask Iv", 

 the extraction arrangement proper J57, and the 

 condensing arrangement Kv, which is put in 

 communication with the water supply. For 

 extraction we employ anhydrous ether. 



To make the experiments we place in a 

 case made of blotting-paper 3-5 gr. of the 

 very finely powdered substance to be em- 

 ployed, which, if rich in fat, it is best to rub 

 up with clean quartz sand. The case we 

 prepare by rolling a piece of blotting-paper 

 twice round a cylinder of wood, whose dia- 

 meter is 4 mm. less than that of the extraction 

 cylinder E, letting the blotting-paper project 

 beyond the base of the wood to a distance 

 equal to the diameter of the latter. We then 

 fold this projecting part as in making up the 

 end of a parcel, and level it by pressing 

 strongly. After filling in the substance, we 

 similarly close the upper end of the case. 

 The filled case is now put for two to three hours into a drying 

 chamber at a temperature of 45 C. Then follows the extraction 

 in the usual manner with ether. Finally the ether is distilled off 

 from the solution of fat in the flask K, and the residue (crude fat) 

 is dried for one to two hours at 95 C., and weighed. 



The fats consist of a mixture of free fatty acids and glycerides. 

 To detect glycerine in these last I proceeded as follows : About 

 75 c.c. of olive oil were digested for a considerable time with 

 d ilute potash solution in a porcelain evaporating dish on the water- 

 bath. After cooling, a large quantity of Sodium sulphate was 

 added to the fluid, the precipitated soap filtered off, and the filtrate 

 neutralised with Sulphuric acid. The fluid was then evaporated, 

 the residue treated with alcohol, the separated sulphates filtered 

 off, and the filtrate again evaporated. The residue was once more 

 treated with alcohol to purify it, and the solution after filtration 



FIG. 111. Apparatus 

 for fat extraction. 



