Page:Philosophical Transactions of the Royal Society A - Volume 184.djvu/348

348 them in about 70 cub. centims. of water. An aqueous solution of ammonia was then added to the copper solution till the deep blue colour was formed. The same volume of ammonia was next run into the ammonium chloride solution, and both were made up to 100 cub. centims. This gave solutions whose strengths were 0.1 monad grm. equivalent per litre. Their specific resistances were found by the method used by and, and came out $$157 \times 10^9$$ (for the CuCl2) and $$117 \times 10^9$$ (for the NH4C1) in C.G.S. units for the cubic centimetre.

The solutions were carefully run into the velocity tubes, and the current sent through them and a low-resistance galvanometer in series. The galvanometer had previously been graduated by sending the current from a single freshly-prepared Daniell cell through it and through a known resistance, and noticing the deflections as the resistance was varied from 11,000 ohms to 150 ohms.

The resistances were then again increased to 400 ohms = 67°.1, 1200 = 45°.9, and 3500 = 18°.7—numbers identical with those first obtained.