150 MASS. EXPERIMENT STATION BULLETIN 167. 



Example. 

 t° = 19.2° C (constant during the experiment). 



Ri =307.0 (constant reading on the bridge at five minute interval). 

 R =500.2 (as above). 

 E. M. F. of the normal element =1.0189. 



Then the total E. M. F. of the chain can be calculated as follows: — 



N.E. = normal element. 

 Ac. = accumulator. 

 X = the chain. 

 1000 = scale on bridge. 



500.2 

 ^ 1000X1.0189 (2) 



500.2 



Substituting (2) in (1), 



_ 307.0 1000X1.0189 

 ^ 1000 500.2 



= 0.6254 volt, which is expressed p. 



Substituting the value for p in the formula, 



p. 0.5 25-0.3377 



^ 0.0577+0.0002(19.2-18) 

 = 4.967 



or in terms of H ion concentration, 



Ph = 4.967 = -4.967 (log. H) 

 10-4-967= 1.0789X10-' 

 H = .000010789 



Besides the apparatus^ listed above, a H-generator was employed, 

 which is a good-sized Kipp's generator used with a series of washing 

 bottles and drying tube, consisting of (a) 30 per cent. KOH, (b) alkaline 

 pyrogallic acid, (c) cone H2SO4 and soda lime in U-tube. Since a consid- 

 erable amount of CO2 is produced during the course of metabolism, the 

 same precaution is taken as with blood. For this purpose Hasselbach's 

 electrode with shaking arrangement is employed. 



In setting up the apparatus special attention should be paid to rigidness, 

 insulation and temperature. In order to meet with these requisites the 

 apparatus was placed on a big central table in the laboratory. First, one 

 dozen large glass rings of the same height were distributed over the top 

 of the table. These supported a thick glass plate on which several blocks 



» This set of apparatus can be obtained from Fritz-Kohler factory in Leipzig, Germany. 



