404 



REPORT 1886. 



Similar experi7nents tvith h-omine. 



The cathode vessel was filled with a solution of potassic bromide containing- 

 30 grammes of salt to 300 grammes of water. Tuhes filled with same AgoSO^ 

 gelatine as before, each 40 centimetres long. 



As in the iodine experiments there was an advance cloudiness, faint but well 

 defined, in advance of the main precipitate. The readings of the position of this 

 are specified in the above table in parentheses. The meaning of it was not cer- 

 tainly made out, but it was provisionally set down as due to impurity. 



Combined experiments on several substances. 



It thus appears that CI, Br, and I all go at about the same rate and about 

 twice as quick as Ba. It remained to see what strontium and calcium do. Calcium 

 is not an easy substance to experiment on ; its sulphate is too soluble. But 

 strontium is sufficiently easy, though not so sharp and well-defined as barium. 

 To make a better comparison six tubes were taken, each 40 centimetres long, filled 

 with the same Ag^SO^ gelatine solution as before, and arranged in multiple arc 

 with the same E.M.F. (about 40 volts) applied to all of them. This is the E.M.F. 

 between the electrodes, and since gas is given ofi" at the carbon electrodes some- 

 thing like three volts must be deducted for polarisation and for resistance of liquid 

 in vessel. But it was not thought probable that absolute results could be of much 

 use when the composition of jelly is so vaguely known. The diameter of tube 

 XIX. was "370 centim. 



Fig. 9. 



BaClz 



SrClz 



The six tubes were arranged as in figure 9 ; the two anode vessels being filled, 



one with BaCl„, the other with SrCl,, and the 

 KBr, and KI, respectively; in each case 10 

 water. 



three anode vessels with NaCl, 

 grammes of salt and 100 cc. of 



