20 LABORATORY WORK IN PHYSIOLOGICAL CHEMISTRY. 



2. To 5 c.c. of this solution add 2 drops of picric acid 

 solution. 



3. To 5 c.c. of this solution add 3 volumes of 95 per cent 

 alcohol. 



4. To 5 c.c. of this solution add MgS0 4 (in substance) 

 to saturation. 



5. To 5 c.c. of this solution add (NH 4 ) 2 S0 4 (in substance) 

 to saturation. 



Note results and see if the precipitation is complete in each 

 case. 



(d) Acidify 10 c.c. of the protein solution with dilute HC1. 



1. To 5 c.c. of this solution add 2 drops of phosphotungstic 

 acid. 



2. To 5 c.c. of this solution add 2 drops of potassio- 

 mercuric-iodide. 



(e) To successive portions of 5 c.c. of the protein solution 

 add a few drops of CuS0 4 ; neutral and basic lead acetate; 

 HgCl 2 ; trichloracetic acid (2-5 per cent solution); Fe 2 Cl 6 . 



Make careful notes of the results of the above reactions 

 and where possible write equations. Decide as to which 

 class of reaction each belongs. 



The use of metallic salts as antidotes in cases of poisoning 

 is based upon these precipitation reactions. 



SIMPLE PROTEINS. 



The group of simple proteins allows of a further subdi- 

 vision into the simple native proteins and the albuminoids. 



The native proteins, as far as it can be ascertained, exist 

 in the fluids and tissues of the body in the same or at least a 

 similar form in which they appear in the laboratory. The 

 albuminoids are chemically closely related but are charac- 

 terized by great insolubility in all neutral solvents. To 



