FATS AND SOAPS 155 



solution containing in one liter one-tenth of a molecular weight 

 of crystallised oxahc acid, H2C2O4.2H2O, in grams. Weigh 

 out two half-gram portions of pure and previously heated sodium 

 carbonate, dissolve each in water, and titrate with the acid, 

 using all the precautions described on p. 71. Does the 

 quantity of acid required correspond with that necessary to 

 form the compound Na2C204 ? 



XXXIII. FATS AND SOAPS 



Organic, like inorganic, acids are able to form ethereal salts 

 with organic hydroxides, i.e. alcohols. There is, for instance, 

 the acetate of ethyl or acetic ether, C2H5.C2H3O2, produced by 

 distilHng a mixture of alcohol, acetate of sodium, and strong 

 sulphuric acid. The most important of these compounds are the 

 oils or fats occurring in animal or vegetable organisms, which 

 generally consist of olein, palmitin^ and stearin, the oleate, 

 palmitate, and stearate of glyceryl. Olein is an oil, while pal- 

 mitin and stearin are solid fats, the latter having the higher 

 melting point ; hence hard fats largely consist of stearin, soft 

 fats of palmitin and olein. Olive oil, sperm oil, and cod-liver 

 oil are rich in olein, human fat and palm oil in palmitin, suet, 

 tallow, and lard in stearin. 



Just as the alcohols and hydrocarbons are distinguished from 

 each other by their boiling points, the fats may be distinguished 

 by their melting points. Procure some pure palmitate and pure 

 stearate of glyceryl. Prepare a few capillary glass tubes from 

 some odd bits of glass tubing, and seal the points. Into the 

 fine end of one of these thrust a minute fragment of one of 

 the pure fats, and attach the tube to a thermometer, as figured 

 (Fig. 50) by means of india-rubber bands. Make a stirring rod 



