FREEZING- AND BOILING-POINTS 331 



when it takes place into distilled water. From the value of the 

 coefficient of diffusion and the viscosity of the liquid into which 

 diffusion occurs, it is possible, employing the formula of Einstein, 

 to compute the relative volumes occupied by the particles of egg- 

 albumin when diffusing into different solvents. Applying this 

 method of computation, Dabrovsky finds that the volume occu- 

 pied by the egg-albumin molecules when dissolved in distilled 

 water is no less than six times as great as that which they occupy 

 when dissolved in a 3.6 per cent solution of ammonium sulphate. 

 The extraordinary diminution of molecular volume which am- 

 monium sulphate brings about must undoubtedly be connected 

 with the high coagulating power of this salt and is probably to be 

 attributed to dehydration of the protein, i.e., to abstraction of a 

 galaxy of associated water-molecules (Cf. Chap. VI, section 6, 

 also this Chapter, section 6). 



5. The Freezing- and Boiling-points of Protein Solutions. — 

 As is well known, the depression of the freezing-point of a solvent 

 which is produced by a dissolved substance is proportional to the 

 osmotic pressure which the dissolved substance exerts in the solu- 

 tion. Similarly, the elevation of the boiling-point of the solvent 

 is proportional to the osmotic pressure of the dissolved substance. 

 Corresponding to the extremely high molecular weights of proteins 

 the osmotic pressures of their solutions (containing practical per- 

 centages of protein) are low, and the depression of the freezing- 

 point and elevation of the boiling-point of water which are brought 

 about by the introduction of protein are small. 



Consequently Sabanejev (112) found that the depression of 

 the freezing-point which is brought about by egg-albumin could 

 be almost entirely accounted for by the (estimated) pressure of 

 the inorganic constituents of the protein, and Sebanejev and 

 Alexandrov (114) estimated from their determinations that the 

 molecular weight of albumin must be at least 14,000 in order to 

 account for the extremely slight lowering of the freezing-point 

 which could be attributed to the protein alone. The proteoses, 

 Sebanejev estimated, also from cryoscopic determinations, to 

 possess a molecular weight of from 2000 to 3000, while the molec- 

 ular weight of the peptones was estimated to be 400 or less (113). 



Tamman (120) measured the difference between the lowering of 

 the freezing-point of the serum of the horse before and after coagu- 

 lating the proteins by heat, and removing them, and found that 



