CHEMISTRY OF THE PROTEIDS CHAP. 



in egg-albumin, which is perhaps not a simple albumin, it falls to 15. 

 Proteids, which contain, besides albumin, other groups with varying 

 constitutions, differ of course more widely, as do also the protamins and 

 many albuminoids. The sulphur percentage differs more greatly, as 

 in keratin it rises to 4 and even 5 per cent, while in certain albumins 

 rich in sulphur it amounts to 2 per cent, but it falls to 0'4 per cent in 

 haemoglobin. 



The molecular formula, calculated from the percentage composition, 

 must be at least doubled in the case of serum-albumin, as the latter is 

 split up by peptic digestion into at least two sulphur -containing 

 portions ; as the sulphur-containing dissociation-product is apparently 

 cystin, which contains two molecules of sulphur, it would appear that 

 the formula given above has to be quadrupled. Hofmeister l assumes 

 even a formula with six atoms of sulphur, which he bases on his 

 experiments on iodisation : 



^450-^720^ 116^6^140' 



This would correspond to a molecular weight of 10,166. For 

 egg-albumin he calculates in a similar manner a molecular weight of 

 5378. The molecular weight of haemoglobin may be determined by 

 two entirely different methods, which is all the more important 

 because hemoglobin may be prepared as an undoubtedly pure, uniform 

 material, for it crystallises with great ease. In the first instance it is 

 possible to calculate from the percentage ratio of the iron and sulphur 

 the least molecular weight. In this way in Bunge's laboratory, 

 Zinnofsky 2 has calculated for horse's blood, Jaquet 3 for dog's blood, 

 and subsequently Hiifner and Jaquet 4 for ox-blood, the least molecular 

 weight as 16,669. From this weight Jaquet calculates for dog's 

 blood the formula : 



The second method of calculating the molecular weight depends 

 on the power haemoglobin has for binding oxygen and carbon-dioxide. 

 Hiifner 4 finds, as 1 molecule of haemoglobin binds 1 molecule of C0 2 , 

 that he obtains the same molecular weight, immaterial whether he 

 determines it by the C0 2 absorbing power of the haemoglobin or by 

 the percentage number of the iron present in the haemoglobin. The 



1 Fr. Hofmeister, Zeitschr. f. physiol. Chem. 24. 159 (1897) ; D. Kurajeff, ibid. 26. 

 462 (1898). 



2 O. Zinnofsky, ibid. 10. 16 (1885). 



3 A. Jaquet, ibid. 14. 289 (1889). 



4 G. Hiifner, Arch. f. (Anat. u.} Physiol. 1894, p. 130. 



