FATS 115 



;. Try the acrolein test as in Exp. 17 b. 



d. Fuse some lecithin in a metal crucible with a fusion mixture of 3 

 parts of caustic potash and i part of potassium nitrate. Dissolve in a 

 small volume of water, acidify slightly with nitric acid, add a few drops of 

 ammonium molybdate solution, and warm to 75 C. for a few minutes. A 

 yellow precipitate of ammonium phosphomolybdate indicates the presence 

 of phosphorus in the lecithin. 



e. Try to saponify some cholesterol as in Exp. 16 c. As cholesterol is 

 not a fat, saponification does not take place. 



20. The Salts. Coagulate the protein in 10 grams of chopped meat or 

 25 c.c. of blood by boiling for a few minutes with 25 c.c. of water to which a 

 few drops of acetic acid have been added. Filter off the coagulated protein, 

 wash the precipitate on the paper with a very little hot water, and add the 

 washings to the original filtrate. The coagulum should filter off quickly 

 and the filtrate should be perfectly clear; otherwise repeat the experiment. 

 Make the following tests: 



a. Chlorides. Acidify a small portion of the filtrate with nitric acid 

 and add a few drops of silver nitrate solution. A white precipitate, which 

 dissolves on adding ammonia and reappears on acidification with nitric 

 acid, shows the presence of chlorides. 



b. Sulphates. Acidify a portion of the filtrate with hydrochloric acid 

 and add a few drops of barium chloride solution. A white precipitate of 

 barium sulphate indicates that sulphates are present. A much stronger 

 reaction can be obtained when the ash or alkali fusion of a tissue is tested, 

 the sulphur in the protein then having been oxidized to a sulphate. 



c. Phosphates. Acidify with nitric acid and then add a few drops of 

 ammonium molybdate solution. Warm in the water-bath at 75 C. for a 

 few minutes. A yellow precipitate of ammonium phosphomolybdate indi- 

 cates the presence of phosphate. 



d. Calcium. Add a few drops of ammonium oxalate solution to a por- 

 tion of the filtrate. A white precipitate of calcium oxalate forms. On 

 microscopic examination this is found to consist of characteristic minute 

 octahedrals. 



e. Iron. Acidify with hydrochloric acid and add a few drops of potas- 

 sium ferrocyanide. A Prussian blue color indicated the presence of iron. 

 Try the reaction on some blood which has been ashed in a crucible and 

 dissolved out in a little dilute hydrochloric acid. The iron is present in the 

 compound protein, hemoglobin, of the red corpuscles. 



/. Magnesium. Tease out some fibers of frog muscle in a few drops of 

 water on a microscope slide and invert a beaker containing a piece of filter- 

 paper moistened with ammonia over it. After a few minutes, examine 

 under the microscope. Characteristic star-shaped or fern-like crystals of 

 ammonium magnesium phosphate will be seen. 



