OF VITAL PHENOMENA 181 



a saturated solution at 37° of the laktam form being .01 mol, 

 and of the laktim form being .0068 mol. The solubility is greatly 

 reduced by the addition of Na salts, which accounts for the fact 

 that it is more than thirty times as soluble in water as in physio- 

 logical salt solution. The primary lithium salt is much more 

 soluble. This has led to the practice of giving lithia water to 

 gouty patients, but it is impossible to decrease the concentration 

 of Na* in the blood to the extent that the solubility of uric acid 

 would be noticeably increased. 



Since uric acid, when added to serum, becomes primary sodium 

 urate, and the solubility of this is very low, it seems strange that 

 the solubility of uric acid in serum should be relatively higher 

 than the urate. According to Schade and Boden (1913), how- 

 ever, the uric acid forms a colloidal solution in serum, and in 

 water, also, under certain conditions. If uric acid is dissolved 

 in water by means of heat and the addition of minute quantities 

 of alkali, a 2 per cent solution may finally be obtained. By the 

 addition of neutral salts or by cooling, the solution may be trans- 

 formed into a transparent gel, which after a greater or less time 

 deposits crystals of uric acid. It is probable that the colloidal 

 solution in serum is protected from crystallization by the other 

 colloids present (protective colloids). 



The blood plasma is very slightly alkaline, this alkalinity being 

 maintained by the bicarbonates (and only to slight extent by 

 phosphates) it contains. Hober (1903 b) was the first to meas- 

 ure the H ion concentration of the blood. The later work on 

 this subject has been largely concerned with the perfection of 

 the technique. It has been shown that the PH of the blood is 

 hardly affected by the changes in temperature to which it is 

 ordinarily subjected (McClendon and Magoon, 1916) and, there- 

 fore, the determinations of the PH of the blood at different 

 temperatures by different observers would be comparable, pro- 

 vided the proper precautions were taken to prevent loss of C0 2 . 

 The technique was described in Chapter IV, 7.5 taken as about 

 the average PH of human blood. The PH of the blood of dif- 

 ferent individuals is so constant as to come almost within the 

 limit of error of measurement. Hasselbalch and Gammeltoft 

 found the PH of the blood of a number of supposedly normal 

 individuals to vary from 7.4 to 7.49. Michaelis (1914) found 



