292 CHEMISTRY OF THE PROTEIDS CHAP. 



are then added different quantities of saturated ammonium-sulphate 

 solutions ; and, finally, by the addition of distilled water all the 

 different mixtures are brought to the same volume. If it is stated 

 that the precipitation-limits for globulin are 2 '9 and 4*6, then is meant 

 that if in 10 ccm. of fluid (globulin + ammonium sulphate + water) 

 there are present 2*9 ccm. of cold saturated ammonium sulphate, that 

 globulin begins to be precipitated, while if 4 '6 ccm. of saturated 

 ammonium sulphate be present, that the precipitation of globulin has 

 come to an end, because the whole of the globulin is precipitated. 

 As the solubility of ammonium sulphate is 76*8 at room-temperature, 

 it is easy to calculate what percentage of ammonium sulphate is 

 required for bringing about incipient and complete precipitation of 

 any one albumin, as soon as we know what amounts of saturated 

 ammonium sulphate have to be added for any given quantity of fluid. 



The boundary lines drawn between individual albumins, by means 

 of fractional precipitation with ammonium sulphate, agree fairly well 

 with those obtained by means of other salts, and the groups of 

 albumins separated from one another by these means show also in 

 other respects great similarity. 



The complex albumins, namely, fibrinogen, casein, and the nucleo- 

 albumins of the cell-plasm, are partially precipitated by even incom- 

 pletely saturated solutions of magnesium sulphate and sodium chloride. 

 The upper precipitation-limits of these substances for ammonium 

 sulphate are 3'0. 



The albumins of the second group, including the different 

 globulins, the mucins, and also the primary albumoses, are only 

 precipitated by completely saturated solutions of magnesium sulphate. 

 The precipitation-limits of this group of albumins lie for ammonium 

 sulphate between 2 '.7 and 4'6. 



The albumins of the third group, including the albumins proper 

 and haemoglobin, are not precipitated by the above salts, except 

 they be used in the combination : magnesium- + sodium-sulphate ; 

 while they are precipitated by almost completely saturated solutions 

 of ammonium sulphate or zinc sulphate. The deutero-albumoses 

 resemble the true albumins, but it is possible to subdivide them still 

 further by means of fractional precipitation, as has already been 

 pointed out on p. 179, where the researches of Pick and Haslam have 

 been described. 



Fuld and Spiro, 1 Forges and Spiro, 2 Joachim, 3 and Freund and 



1 E. Fuld and K. Spiro, Zeitschr. f. physiol. Chem. 31. 132 (1900). 



2 0. Forges and K. Spiro, Hofmeisters JBeitrdge, 3. 277 (1902). 



3 J. Joachim, Wiener klinische Wochenschrift, 1902, Nr. 21. 



