FAT ACIDS 99 



bulb of a thermometer at the same level. Mount the test tube with the 

 thermometer in a beaker on a ring stand, fill the beaker with water above the 

 level of the content of the test tube, and gradually heat with stirring of the 

 water in the beaker. At the melting temperature the flake of fat will run 

 into a round drop. 



b. Solubility. Fat is insoluble in water, but soluble in ether, chloro- 

 form, benzol, and in alcohol. 



c. Saponification. Heat some fat in an evaporating-dish, add sodium 

 hydrate, and boil. Saponification takes place. The soap is soluble in water. 

 Add 25 per cent sulphuric acid to some of the soap, the fatty acid is liber- 

 ated and collects on the surface of the solution. 



13. Fat Acids. Collect some of the fatty acids, wash to remove 

 excess of alkali, and dissolve in ether. 



a. Acid reaction. Add ether solution of the fatty acid to neutral litmus, 

 or to faintly alkaline phenolphthalein. The former turns red, and the red of 

 the latter is discharged, the acid reaction. 



b. Acrolein test. Evaporate the ether from 2 c.c. of the solution, add 

 potassium bisulphate crystals to the acid in a test tube, and raise to a high 

 heat over a bunsen. No acrolein is given off. Repeat on neutral fat and 

 on glycerin. Both liberate the irritating fumes of acrolein. 



14. Emulsification. a. Shake up neutral olive oil and water, no 

 emulsion is formed and the oil quickly separates. 



b. Add a couple of drops of fatty acid, a very good but temporary emul- 

 sion is now formed. 



c. Use rancid fat, a temporary emulsion is formed. 



d. Add a little soap to either of the above, i.e., c. A good permanent 

 emulsion is now formed. 



15. The Salts. A goodly series of salts is present in the body, 

 the most important elements of which are sodium, potassium, calcium, mag- 

 nesium, and iron, as chlorides, sulphates, and phosphates. Burn 50 c.c. of 

 blood at a dull red heat, take up in water and test: 



a. Chlorides. Add i per cent nitrate of silver, a white precipitate, in- 

 soluble in nitric acid, soluble in ammonia, and reprecipitated by nitric acid. 



b. Sulphates. Add barium chloride, a white precipitate, which quickly 

 settles and is insoluble in nitric acid. 



c. Phosphates. Add nitric acid and a few drops of i per cent ammonium 

 molybdate, a yellow granular precipitate of phosphorus. It is soluble in 

 ammonia, reprecipitated in nitric acid. 



d. Calcium. Make a hydrochloric acid extract of the ash of blood 

 above, add ammonia to excess, then a solution of ammonium oxalate, a deli- 

 cate white precipitate where traces are present. 



e. Iron. Add hydrochloric acid and a few drops of ferrocyanide of po- 

 tassium. A blue color indicates the presence of iron. 



