vin DENATURALISED ALBUMINS 345 



investigated. It is prepared by precipitating egg-albumin with salts 

 of copper ; l dissolving the copper-albuminate in alkalies ; precipitating 

 it by careful neutralisation, and repeating this process several times. 

 In this way it is possible to obtain a compound containing very little 

 ash. It is, according to Biilow 2 and Werigo 3 an acid-albumin, a 

 chloride of denaturalised albumin. Harnack's albumin illustrates 

 very well the properties of denaturalised albumin. It is soluble in 

 acids and alkalies in the absence of salts, while in acid solutions it is 

 precipitated at once by the addition of salts. Its equivalent numbers 

 are referred to on p. 329. It gives all the reactions of albumin except 

 the lead-sulphide reaction, notwithstanding the fact that it contains the 

 full complement of sulphur. Harnack explains this phenomenon by 

 assuming a partial oxidation, and he calls the ash -free albumin 

 ' anoxidised/ Its heat of combustion is stated by Stohmann and 

 Langbein 4 to be 180 calories lower than that of native albumin, but 

 these figures are of little value considering that neither normal 

 albumin nor ash-free albumin are quite pure bodies. 



Other examples of denaturalised albumins are the halogen com- 

 pounds, the oxyprotein and oxyprotsulphonic acid, the methylene- and 

 ethylene-albumins, all of which it is impossible to coagulate (see 

 index). The substances just mentioned resemble Harnack's albumin 

 in not giving the lead -sulphide reaction at all, or only to a slight 

 extent. What causes this change in the sulphur-radical is not known, 

 but the change is not directly dependent on denaturalisation, for 

 Schulz and others have made their ordinary sulphur determinations 

 mostly on coagulated albumins. 



1 See p. 304 under copper albumin ates. 

 2 K. Billow, Pfiug&rs Arch.f. d. gesamte Physiol. 58. 207 (1894). 



3 Br. Werigo, ibid. 48. 127 (1891). 

 4 F. Stohmann and H. Langbein, Zeitschr. /. prakt. Chem. (2) 44. 336 (1891). 



