X, A, 1 Pratt: Papain 5 



coagulated egg albumen in 0.10 per cent sodium hydroxide 

 solution, while others advocate fibrin, etc. The duration and 

 temperature employed also vary greatly. No systematic inves- 

 tigations have been made that enable one to form a. logical 

 opinion regarding the digestive powers of papain ; the optimum 

 conditions of temperature, alkalinity, or acidity; the rate of 

 digestion; etc. 



It was greatly to be desired that some method for analysis 

 be found which would give accurate results without requiring 

 elaborate apparatus or laborious manipulation and that would 

 not depend upon some sample of papaya gum arbitrarily se- 

 lected as a standard. Methods depending upon the comparative 

 volumes of undigested material are not trustworthy, and those 

 in which it is necessary to determine the increase in soluble 

 nitrogen during digestion are not only unsatisfactory, but also 

 exceedingly tedious when many analyses have to be made. 



The following scheme for assaying papain has given satis- 

 factory results in many hundreds of cases, and may be recom- 

 mended as simple, rapid, and accurate. It has the advantage 

 of being carried out readily in any laboratory, and gives all 

 the information necessary for determining the quality of the 

 sample. 



METHOD FOR THE ANALYSIS OF PAPAIN 



Milk, as nearly as possible free from butter fat, is the most 

 satisfactory material to employ as substrate. The various well- 

 known brands of condensed skimmed milk possess reasonably 

 constant composition, and are well suited to the purpose. I 

 employed a 40 per cent solution of sweetened condensed skimmed 

 milk in the analyses recorded in this paper, not only because 

 fresh skimmed milk was not procurable in Manila, but also for 

 the reason that the canned milks keep well and are thus always 

 available. 



The enzyme solution was prepared by dissolving 0.75 gram 

 of powdered papain in 150 cubic centimeters of distilled water. 

 Papain is not completely soluble in water, but by warming the 

 mixture for thirty minutes in the thermostat at 40° the active 

 principle is dissolved and upon filtering a clear solution is ob- 

 tained. Well-prepared gums give a colorless filtrate, which is 

 slightly acid and shows a marked tendency to froth. The di- 

 gestions were carried out in 150 cubic centimeter Erlenmeyer 

 flasks. The volumes of milk, water, and papain solution used 

 may be seen from Table I. 



