180 PHYSICAL CHEMISTRY 



of the corpuscles and to a less extent by the proteins of the 

 plasma. The normal viscosity is 4.05-6.8, is greater in man than 

 in woman, and increases after feeding and after muscular work. 

 In cardiac insufficiency it may reach 8.1 and in polycythemia 

 14.4-23.8. It is also increased by stasis. A convenient viscosi- 

 meter for blood is shown in Fig. 29. (It may be obtained from 

 A. S. Jones, Princeton, N. J.) 



The fact that the viscosity of the blood is determined chiefly 

 by the total volume of the corpuscles suggests a method of deter- 

 mining the corpuscular volume. Such measurements must be 

 made at nearly the same temperature, to be comparable. The 

 viscosimeter is standardized with H 2 at the temperature at 

 which the blood is investigated, but the absolute viscosity of water 

 is 27 per cent less at 37 than at 17 whereas this ratio is not the 

 same for blood (blood is said to be 16 per cent less viscous at 37 

 than at ij° but it is not clear that the absolute viscosity is meant). 

 According to Hess the hemoglobin may be calculated as follows : 



hemoglobin 



— ; ; =19, except in diseases in which the hemoglobin 



viscosity 



content of the corpuscles or the plasma proteins or the proportion 

 of leucocytes is changed.- 



The normal refractive index of the serum of man is 1.345-1.35. 

 According to Pearl (1914) the refractive index of the serum of 

 the fowl is 1.34537 and of the guinea hen 1. 34184. 



It is usual to consider the solvent power of the blood plasma 

 as being nearly the same as that of water, but this is not always 

 the case. Uric acid is practically insoluble in water, the con- 

 centration of its saturated solution at 18 being .00015 mol, the 

 molecular weight being 168.2. Bechhold and Ziegler (1910) 

 found that a liter of serum would dissolve more than half a gram 

 of uric acid, at 37°, showing that its solubility in serum is enor- 

 mously greater than in water. The reason for this difference is 

 not self evident. Uric acid is a weak acid, in saturated solution 

 in water being only 9.5 per cent dissociated. Although theoret- 

 ically a dibasic acid it acts like a monobasic acid, as only one H 

 ion is dissociated ordinarily. The primary sodium salt is more 

 soluble than the free acid in water because it is strongly disso- 

 ciated. According to Gudzent (1909 a) there are two isomeres, 



