448 CHEMISTRY OF THE TISSUES. 



spirit becomes warm, part of the oil will be dissolved. Pour 

 oil' some of the clear alcoholic solution into another tube and 

 cool it. It will become milky from the deposition of oil. f 4. 

 Cold ether. Shake a little oil with ether and it will dissolve 

 readily. The test-tube containing the ether must not be 

 brought near a flame, as its vapor is readily inflammable. 5. 

 Chloroform ; 6. Oil of turpentine, and other volatile oils, also 

 dissolve fat readily. 



* Emnl*inni*ing of Fats. Shake a little oil with a solution 

 of albumin in a test-tube. The oil will become finely divided, 

 and form a milky-lookiug fluid or emulsion. Put a drop of 

 this under the microscope, and it will be found to consist of 

 minute globules of fat. The globules in the emulsion unite 

 again and form large globules, but very slowly. Add a little 

 acetic acid to the emulsion and shake it. The globules will 

 unite much more quickly. Repeat the experiment with a solu- 

 tion of gelatin. This also will emulsionize the fat. 



Reaction. Wash a piece of lard in water and press a piece 

 of litmus paper against it, or melt it in a test-tube, and put a 

 drop of it or of olive oil on the paper. Its reaction will be 

 neutral. 



Composition of Fate* Fat consists of a triatomic radicle, 

 propenyl or glyccryl, combined with three atoms of ;i inona- 

 toinic fatty acid. The glyceryl may be displaced by inorganic 

 bases, such as potassium, lead, etc., and glyceryl hydrate, or 

 glyccryl alcohol (glycerin) is produced. The replacement of 

 glycerin by other basis is termed saponification. 



Boil two and a half grammes of olive oil with one gramme 

 of very finely powdered lead oxide, and about fifty cubic centi- 

 metres of water in a beaker or evaporating dish for some 

 hours, stirring the mixture well to prevent the lead oxide from 

 tailing to the bottom, and replacing the water as it evaporates.. 

 The lead will combine with the fatty acid in the oil, forming a 

 slightly yellowish mass, and the glycerin will be set free. To 

 obtain the glycerin, filter the fluid : pass sulphuretted hydrogen 

 through the filtrate, add a little animal charcoal to decolorize 

 it : let it stand for a while in a warm place; filter and evapo- 

 rate the filtrate. 



i - 54. Glycerin. Glycerin is a syrup^y fluid, with a sweet 

 * taste ami a neutral reaction. 



Xohihilifi/. 1. With water, and, 2. with alcohol, it mixes 

 very readily, o. With ether it does not. 



Xi,ft' t -iif i'mi-er It dissolves many metallic oxides. Add a 

 little liquor potnssje to a solution of copper sulphate or lead 

 te, a precipitate will fall. Add a little glycerin, and the 

 precipitate will redissolve. 



It aUo acts to some extent as a solvent for fatty acids. 



/' composition. Put a little glycerin, free from water, into 



