272 Prof. Potter. Electrical Effects accompanying the [July 14,, 



Thus, a study of this cell when charged with dilute sulphuric acid and 

 zinc, or with water and either phosphorus or potassium or sodium, gains- 

 importance from its bearing upon the action of yeast and glucose in a 

 similar cell. It has been proved that the principle of this special type of 

 cell is equally applicable to the two cases, and the results obtained are 

 precisely analogous in both sets of experiments. For the purposes of the 

 present research it is sufficient to have established this point, to note that 

 an E.M.F. is developed in these special cells, and that the centre of chemical 

 activity with platinum electrodes is always zincative. 



Non-pola risablc Electrodes. 



The behaviour of non-polarisable electrodes in a cell of this construction is 

 also of much interest, and an exact parallel is found between the action of 

 these electrodes when used in conjunction with either a yeast-glucose or a 

 zinc-sulphuric acid cell. 



The non-polarisable electrodes consisted of a glass U-tube, plugged at the 

 bend with kaolin ; into one limb of this tube a saturated solution of zinc 

 sulphate was poured and a rod of amalgamated zinc inserted, the zinc being 

 connected with the condenser and galvanometer leads. Into the other limb 

 was placed a solution of glucose or of sulphuric acid of the same concentra- 

 tion as that employed in the cell, and a lamp wick soaked in the glucose or 

 sulphuric acid solution was arranged so that one end of it dipped into 

 the U-tube and the other into the cell. 



Another form of non-polarisable electrode consisted of a pair of glass 

 tubes, closed at one end either with a plug of kaolin or with a piece of 

 bladder tied tightly round. These tubes were partially filled with the zinc 

 sulphate solution, into which dipped a rod of amalgamated zinc. One of the 

 tubes was inserted into the outer and the other into the inner fluid of 

 the cell, and the connections were made with the condenser-galvanometer 

 circuit as before. 



Such electrodes, when used either with a yeast-glucose cell or a zinc- 

 sulphuric acid cell and the condenser, gave no deflections upon the galvano- 

 metric scale. In both these cases, however, the existence of an electric 

 current, depending upon the resistance of the circuit, can be shown by 

 connecting the leads from the non-polarisable electrodes directly with the 

 galvanometer. The electrical action is developed both in the yeast-glucose 

 and in the zinc-sulphuric acid cells, as shown by the current generated, but 

 the condenser method is not applicable with the use of non-polarisable 

 electrodes. 



As a further test of this principle, cells were set up with a pair of 



