40 E. J. STIEGLITZ 



were able, however, to procure a less toxic form of ferric ammo- 

 nium citrate from Parke, Davis & Co., in the form of green 

 scales. This salt caused no immmediate toxic symptoms, even 

 when as much as 0.8 gram was injected intravenously into a 

 2-kg. rabbit. In most of the subsequent experiments this 

 form of ferric salt was used. For some time we were unable to 

 get this product, and tried Merck's green salt, but found that it 

 too was toxic in much the same manner as the brown scales. 

 Several experiments were carried out to determine the chemical 

 differences between these salts in an attempt to explain their 

 marked difference in behavior in animal experimentation. It 

 was at first suspected that the difference was due to some free 

 ammonia in the brown salt because of the similarity of the symp- 

 toms to ammonia intoxication as recorded by Rachford and 

 Crane (45). But the quantitative chemical analyses proved this 

 supposition to be incorrect. Experiments K23, K44, K45, K48 

 are included in this series. The brown salt is described in the 

 United States Dispensatory and the United States Pharma- 

 copoeia as having about 16 per cent of iron. On analysis it was 

 found that the green salt contained 16.4 per cent iron. The 

 ammonia determination, by the Kjeldahl method showed the 

 brown salt to contain 5.7 per cent NH4, and the green 8.8 per 

 cent. These percentages then show that the more toxic salt 

 contains the smaller amount of ammonia. The composition of 

 the two salts can be roughly calculated from these results. 



Taking for the green salt the composition as being two ferric citrate 

 molecules plus one of triammonium citrate, the calculated percentages 

 are 7.3 per cent for ammonia and 15.2 per cent for iron. Therefore: 



Calculated NH4 = 7.3 per cent. 



Analysed NH4 = 8.8 per cent. 



Calculated Fe = 15.2 per cent. 



Analysed Fe = 16.4 per cent. 



This checks as closely as need be for the purity of a commercial 



products. In the same way, if we take two ferric citrate molecules, 



plus one of diammonium citrate, for the brown salt, the calculated 



percentages are: 5.03 per cent for NH4 and 15.65 per cent for iron. 



Therefore : 



Calculated NH4 = 5.03 per cent. 



Analysed NH4 = 5.7 per cent. 



Calculated Fe =15.65 per cent. 



Analysed Fe = 16.0 per cent (U. S. Dispensatory). 



