Mr. J. Napier on Electrical Endosmose, 15 



transferred more or less from the positive to the negative elec- 

 trodes by endosmose, and that the amount of this varies ac- 

 cording to the texture of the porous diaphragm, the power of 

 the electric current, and various other modifying circum- 

 stances, which will be apparent as we proceed with the inquiry 

 into the cause and circumstances of electrical endosmose. 



In referring to the first experiment, it was observed that the 

 greatest amount of measurable endosmose took place during 

 the last ten hours when both solution and battery were nearly 

 exhausted. 500grains of sulphate of copper were again put into 

 each cell, the solutions accurately measured, and the current 

 of 9 pairs passed for twenty hours. The deposit on the negative 

 electrode was 116*3 grains; this solution had increased in 

 measure three-eighths of an ounce, the positive had lost half 

 an ounce ; being evaporated and crystallized, the negative gave 

 226 grains crystals, the positive gave 749 grains. In this ex- 

 periment we have 184 grains of the salt transferred, and only 

 three-eighths of an ounce of measurable endosmose. 



960 grains of sulphate of copper were dissolved in 20 ounces 

 of water and put into the negative cell, while the positive was 

 charged with dilute muriatic acid. A battery of 12 pairs 

 was connected and kept in action twenty-four hours ; it was 

 then found that the negative electrode had increased in weight 

 178 grains, and the solution had gained in measure 2^ ounces. 

 A small portion had nitrate of silver added, which gave a slight 

 milkiness, but not amounting to a precipitate. The whole solu- 

 tion of the negative cell, being evaporated and crystallized, gave 

 sulphate of copper 463 grains. This shows a transfer of sul- 

 phate of copper from the positive solution equal to 162 grains. 

 The positive solution was of a deep blue colour, it had lost 

 by measure 2^ ounces ; the electrode was covered with a 

 white powder, and had lost 212 grains. Here again the two 

 kinds of endosmose are perfectly distinct. But we have another 

 curious result, viz. the muriatic acid apparently refusing to 

 be transferred from the positive to the negative solution. This 

 attracted particular attention, and the next experiment was 

 conducted in the following manner: — 100 grains of sulphate 

 of copper were dissolved and put into a small porous vessel, the 

 solution measuring 2~ ounces; this was supported at the top 

 of a deep glass vessel filled with dilute muriatic acid, so that 

 several inches of solution were under the porous vessel, the 

 surface of the two solutions being level; by this arrangement 

 the copper salt formed at the positive electrode by the cur- 

 rent sunk to the bottom by its own gravity and remained un- 

 der the porous vessel, so that no transfer of salt could take 



