368 Soi&ntifto Intelligence. 



tin' first, and this leads to Pb t b as the formula for" the higher 

 electrolytic oxide estimated in situ. 



For lack of space we shall pass over the remaining lines of 

 evidence and quote the author's conclusions, which arc: 



1. The behavior of the lead accumulator while discharging is 

 identical with that of a primary cell with a solid depolarizer, "the 

 manganese cell for example; with this difference that the nega- 

 tive electrode gives rise to an insoluble salt. 



2. The theory of "double sulphating" is manifestly inexact 

 and the reaction during normal discharge is given by: 



(a) Pb + Jf t SO^+ PlK t O, = PbSO t + 77 2 6> + ZPbO„ 

 or possibly 



(b) Pb + i/ 2 so 4 + Pb,o t = Pbso, + 11,0 + 2Pbo r 



Formulas (a) and (b) lead to masses of 15 and 10-4 grams of 

 the higher oxide per ampere-hour respectively, the best commer- 

 cial tests giving values of the same order, namely 12 to 14 for 

 thin plates slowly discharged. 



3. The quantity of acid combined during discharge is exactly 

 one-half of that indicated by the theory of "double sulphating." 



4. The variations in mass of the positive plate must be very 

 small and in the opposite sense to those predicted' by the theory 

 of "double sulphating." 



5. The mass of lead to use for the positive electrode must be 

 exactly double that taking part in the reaction at the negative 

 grid if the formula Pb„ O h be accepted. 



6. When discharged the active material of the positive plate 

 becomes lead dioxide. — -lour, de Phys., Jan. -Feb., 1916, p. 21. 



h. s. u. 



6. An Active Modification of Nitrogen. — In his six earlier 

 papers on this gas R. J. Strutt has dealt primarily with the 

 properties of active nitrogen when once produced. The seventh 

 contribution, now under consideration, pertains chiefly to the 

 circumstances of its production by the electric discharge. 



With this object in view it was necessary to abandon the very 

 efficient but complicated jar discharge and make use of the direct 

 current furnished by three motor-driven magneto generators 

 joined in series. At full speed the output was 15 milliamperes at 

 5000 volts. The gas used in the experiments was commercial 

 bomb-nitrogen which was kept for a time over phosphorus and 

 then dried by the pentoxide of this element. At least seven dif- 

 ferent forms of discharge tube were employed in the investigation 

 so that it will not be possible to describe the apparatus in this 

 place. The results obtained may be summarized as follows : 



J. The production of active nitrogen in the steady discharge 

 is a maximum near the cathode, it falls to a minimum in the 

 Faraday dark space, and increases again in the positive column 

 until a value is attained which stays constant throughout the 

 remaining: length of this column but which is less than that at 

 the cathode. 



2. When the amperage is kept unchanged, a much larger 

 quantity of active nitrogen is obtained from the positive column 



