92 PHYSIOLOGICAL CHEMISTRY. 



Acid Albumin. According to the view held at one time the 

 solution of the alkali albuminate in water yields an acid albu- 

 min on acid treatment. But the weight of evidence now indi- 

 cates that the group in the albuminate having an acid function 

 is different from the group in the so-called acid albumin which 

 certainly plays the part of a basic radical. Although the 

 albuminate and the acid albumin have certain points in com- 

 mon, as will be shown, they are not identical. It appears, 

 however, that while the albuminate may not be converted into 

 acid albumin by action of weak acid, the opposite conversion 

 is possible; that is, weak alkali will change acid albumin into 

 albuminate. Some simple experiments may be made here: 



Ex. Dilute white of egg with four volumes of water, take 25 cc. of 

 the mixture, add 5 cc. of 0.2 per cent hydrochloric acid and warm it on 

 the water-bath for about two hours to a temperature of 45 C. Then care- 

 fully neutralize the solution with dilute sodium hydroxide, using phenol- 

 phthalein as indicator. This precipitates insoluble acid albumin, which 

 can be washed with water by decantation. It is essential that just the 

 right amount of alkali be added here ; an excess would redissolve the pre- 

 cipitated acid albumin with formation of alkali albuminate. The washed 

 acid albumin can be used for a number of tests. 



Ex. Dissolve a little of the washed acid albumin in water by the aid 

 of weak hydrochloric acid, and note that the solution does not coagulate 

 on boiling. Observe, however, that the addition of common salt to the 

 acid solution brings about precipitation. The same thing was found to 



be true with the solution of alkali albuminate in acid. 



\ 

 In forming acid albumin from a native albumin the action 



of the weak hydrochloric acid employed is much less destruc- 

 tive than is the action of the alkali in producing albuminate. 

 The actual modification of the protein molecule is much less 

 profound. Nothing is split off as is the ammonia or hydro- 

 gen sulphide in the other case, and this may account for the 

 observed fact that the acid albumin may be changed into albu- 

 minate by use of weak alkali. It must of course be remem- 

 bered that a stronger acid may not be used in making the acid 

 albumin, since here too the reaction may become destructive. 

 SYNTONIN. This appears to be an acid albumin, resulting 

 from the action of dilute acids on muscle, and is very readily 



