612 



EXPERIMENT STATION RECORD. 



tVol. 43 



gas is libornted it rises vertically in the closed ai'iii without appreciable loss 

 through the bulh. The introduction of a small quantity of rather coarse, acid- 

 washed sand into the depression is suggested as aiding materially the liberation 

 of the gas. 



It is stated that with the same inoculum the volume of gas liberated within 

 a given time is about three times as great with the modified tube as witli the 

 ordinary Smith type. 



Electrodes of platinized glass for electrolytic determinations, G. Meilt.ere 

 (Jour. Pharm. et Chiin., 7. ser., 21 {1920), No. 8, pp. 311-313).— The author sug- 

 gests the substitution of platinized glass in place of platinum for electrodes. 



The glass is platinized by covering it with a thin coating of platinic chlorid 

 in oil of turpentine or some other essential oil to which methyl alcohol has 

 been added to render the mixture more fluid. On heating, the platinic clilorid 

 is reduced to metallic platinum, forming a thin coating on the glass. 



Acidity and acidimetry of soils. — IT, Investigation of acid soils by means 

 of the hydrogen electrode, H. G. Knight (Jour. Indus, and Enffin. Cliem., 12 

 (1920), No. 5, pp. 4^7-JfG4, flgs. 8). — In continuation of the investigation pre- 



2 4 e a 10 cm, 



1 I I I I I 



Fig. 1. — New hydrogen electrode cell for continuous agitation. 



viously noted (E. S. R., 43, p. 12), the author presents the results of a study 

 of (1) the speed of reactions between neutral salt solutions and .soils, (2) 

 the speed of reactions in the presence of a base, (3) the change in H-ion con- 

 centration with change of amount of base and with time, and (4) the change 

 in conductivity of soil solutions. 



A special gas cell which could be agitated continuously was designed for the 

 work. The essential features of the apparatus as shown in the accompanying 

 diagram (fig. 1) are as follows: 



The calomel electrode A is connected by means of the stopcock B with a 

 U-tube C filled with n KOH, w^hich in turn is connected with the hydrogen 

 gas cell by the tube D. The gas cell E is cylindrical in sliape, 3.3 by 16 cm., 

 with rounded ends. The hydrogen enters through the tube F, which extends 

 nearly to the bottom of the cell. A short outlet tube G and the electrical 

 connection H also pass through the same rubber stopper. The apparatus 

 is placed on a tilting table I hinged at the point J to the base K. The 



