238 SOAPS AND PROTEINS 



prepared is shown in the upper row of Fig. 111. The tube on the 

 left contains the gelatin-water control, the remaining tubes 

 gelatin and silver nitrate. There was now added to the tubes, 

 respectively from left to right, 5 cc. water, 5 cc. water, 5 cc. m/3 

 sodium sulphate, 5 cc. m/3 magnesium sulphate, 5 cc. m/10 

 potassium hydroxid. The lower row of Fig. Ill shows the effects 

 of such treatment thirty-six hours later. The first two tubes 

 are obviously unchanged. There has been distinct recession of 

 the coagulating effects of the silver in the remaining tubes, restitu- 

 tion in the case of the KOH being apparently complete. 



FIGURE 111. 



Fig. 112 shows the reversing effects of these and other lighter 

 metal salts when added to a series of 2 percent gelatin solutions 

 (5 cc. each) previously coagulated through the addition of an 

 equal volume of m/500 cupric sulphate, m/1500 ferric sulphate, 

 m/1000 plumbic chlorid. After the coagulants had acted for 

 forty-eight hours the reversing agents (5 cc. each) were added 

 to the tubes (m Nal, 2 m MgCl 2 , m/20 KOH, 2 m KC1, 2 m 

 MgCl 2 , m/20 KOH, 2 m KBr, 2 m KC1, m/20 KOH). The 

 photograph portrays the tubes twenty-four hours after such addi- 

 tion. The clear gelatin control appears on the extreme left. 

 The unchanged heavy metal controls are the left-hand tubes in 

 each of the remaining groups. The three remaining tubes of 



