212 PHYSIOLOGICAL CHEMISTRY 



acetic acid prepared, and boil for 2-3 minutes, stirring with a 

 glass rod. If the liquid does not clear, add 3-4 drops more of 

 the acid and boil again. Observe the mixture closely, as the 

 liquid may be quite clear, but appear cloudy from the large num- 

 ber of solid particles suspended in it. Repeat the addition of 

 acid and boiling if necessary. Caution : Addition of too much 

 acid will cause the solution to be muddy in appearance, so that 

 it will not filter clear. This treatment dissolves out a large part 

 of the inorganic salts, and coagulates the protein material. 

 Filter the liquid from the solid residue. Test the filtrate for 

 inorganic materials as described below in Section III. 



2. Muscle Residue. The coagulated protein material and 

 connective tissue also contain inorganic substances, but in 

 organic combination. To detect them it is necessary to destroy 

 the organic compounds by fusion with an oxidizing agent. 



Wash the coagulated muscle residue with a little hot water 

 and dry it by pressing between filter papers. Half fill a crucible 

 with fusion mixture. This is a basic oxidizing agent which con- 

 tains KN0 3 and NaOH. The nitrate furnishes nascent oxygen, 

 and the sodium hydrate prevents loss by volatilization of in- 

 organic substances, excepting a portion of the carbonates. 



Support the crucible in a clay triangle and melt the fusion 

 mixture (hood) by heating cautiously with the Bunsen flame. 

 Add small portions of the muscle residue until the charred par- 

 ticles do not disappear on heating carefully. When this point 

 has been reached, add a few crystals of fusion mixture, and heat 

 until colorless. Allow the crucible to cool and dissolve the 

 residue in water acidified with nitric acid. The volume should 

 not exceed 100 c.c. Test the solution with litmus (it should be 

 acid) and make phosphate, sulphate and iron tests as described 

 below in Section III. What do you conclude as to the forms in 

 which phosphorus, sulphur and iron are present in muscle 

 tissue ? 



3. Blood Serum. Heat 100 c.c. distilled water to boiling, 

 acidify with a few drops of \% acetic acid and pour into it 

 slowly 20 c.c. blood serum or blood. The liquid should be faintly 



