Insulin 



415 



that throws down a precipitate from aqueous solution but leaves 

 the insulin in solution. Eight of the nine remaining reagents 

 have given consistent and good positive precipitations. Of these 

 ammonium sulphate is the only inorganic reagent and our re- 

 sults with it have been far from startling, although Shaffer 

 claims that by means of one-half saturation with it insulin is 

 thrown out of solution in the globulin fraction. Acetone, tri- 

 chloracetic acid and the six alcohols, methyl, isopropyl, n-propyl 

 n-butyl, n-amyl, and n-caprylic have rarely failed to yield a 

 potent precipitate. 



In the table all potency values except the first few represent 

 the drop in the blood sugar of the normal rabbit brought about 

 in a period of two hours by the injection of the equivalent of 

 2 c.c. of the original or 20 gms. pancreas. 



table I. 



EFFECT OF PRECIPITATION ON POTENCY* 



Extract 

 No. 



Precipitant 

 5 vols, added 



Original 

 Potency 



Potency of 

 precipitate 



Potency of 

 filtrate 



84-2 



Absolute alcohol 



—.045 



+ .017 



—.085 



84-2 



A cetone 



—.045 



—.034 



it. 000 



84-2 



Toluene 



—.045 



—.003 



—.029 



84-2 



Chloroform 



—.045 



—.013 



—.004 



75-3 



Absolute alcohol 



—.061 



—.010 



—.070 



75-3 



Ether 



—.061 



+ .011 



—.018 



75-3 



Chloroform 



—.061 



—.015 



—.001 



87-3 



Acetone 



—.047 



—.036 



—.009 



87-3 



Acetone reppt. 



—.047 



—.049 





101AB 



n-Butyl alcohol 



—.072 



—.075 



—.081 



101AB 



n-Amyl alcohol 



—.072 



—.082 



+ .003 



105 



Trichloracetic 



—.087 



—.069 



+ .003 



106B 



n-Butyl alcohol 



—.028 



—.039 



—.003 



106B 



n-Amyl alcohol 



—.028 



—.052 



—.009 



106B 



n-Caprylic alcohol 



—.028 



—.050 





114A 



Trichloracetic 



—.007 



—.046 





114A 



Ammonium sulphate 1 



—.007 



—.030 





1201 



n Butyl alcohol 



—.056 



— .057 





1201 



n-Propyl alcohol 



—.056 



—.071 





1201 



iso-Propyl alcohol 



—.056 



—.041 





1201 



Methyl alcohol 



—.056 



—.056 



—.004 



1201 



Methyl alcohol 



—.056 



—.033 



+ .003 



119 III 



Ammonium sulphate* 



—.037 



—.024 





119 III 



Ammonium sulphate 2 



—.037 



—.013 





119 III 



Magnesium sulphatel 



—.037 



+ .015 





119 III 



Magnesium sulphate 2 



—.037 



no ppt. 





119 III 



Sodium chloride 1 



—.037 



+ .012 





119 III 



Sodium chloride 2 



—.037 



—.051 





119 III 



Sodium sulphate^ 



—.037 



.000 





119 III 



Sodium sulphate 2 



—.037 



+ .010 





i one-half saturation 2 complete saturation 



* These results are chosen at random. They are not to be taken as bases 



for the conclusions, a complete report at the present time requiring more 

 space than its value would warrant. 



