PROCEEDINGS 
OF THE 
ROYAL SOCIETY OF EDINBURGH. 
vol. ix. 1876-77. No. 99. 
APPENDIX. 
(The MSS. of the following papers were unfortunately mislaid , so that 
the titles only were printed in last years “ Proceedings 
3. The Thermo-Electric Properties of Cobalt, By Messrs 
C. G. Knott, J. Gordon MacGregor, and C. Michie 
Smith. 
(Read 5th June 1876.) 
As we could not find pure cobalt for sale in the state of foil 
or wire suitable for thermo-electric experiments, we resolved to 
prepare it by electrolysis of chloride of cobalt in the way recom- 
mended by Mr Gr. W. Beardslee of Brooklyn, N.Y.* For this 
there is required pure chloride of cobalt of a certain strength 
to form the electrolyte, and spongy metallic cobalt to form the 
positive electrode. By the kindness of Dr Crum Brown these 
were prepared with very great care in the chemical laboratory by 
Mr Robinson, to whom we are much indebted. The following 
note of the method of preparation employed has been supplied by 
Mr Robinson : — 
“Oxide of cobalt was dissolved by heat in hydrochloric acid; 
the acid solution was treated with ammonia in great excess, the pre- 
cipitate at first formed being then dissolved ; the ammoniacal 
solution of chloride of cobalt was then oxidised by passing clean, 
dry air through it till the colour was no longer altered, i.e., till the 
purple colour was succeeded by a reddish-brown, and till it 
admitted of precipitation by hydrochloric acid. This was done, 
* Les MondeSy vol. xxxv. p. 206. 
3 K 
VOL. IX. 
