270 Proceedings of Royal Society of Edinhiirgh. [april 2, 
the analysis, the solution of these crystals was made neutral by the 
addition of a few drops of sodium carbonate solution, a small 
quantity of sodium acetate added, and the zinc then precipitated by 
sulphuretted hydrogen gas. The precipitate was dissolved in 
hydrochloric acid, and the zinc reprecipitated by sodium carbonate. 
Before being thrown on the filter, the precipitate was boiled re- 
peatedly with water, the water being decanted after each boiling. 
In some cases the ignited oxide had to he extracted with boihng 
water, it not being quite free from sodium carbonate. 
The manganese in the filtrate was precipitated as carbonate, and 
similarly treated. 
III. Copper-Iron-Ammonium Sulphate. — Only one crop was 
collected for analysis. 
IV. Copper - Iron - Ammonium Sulphate. — 11 grammes (*04 
equivalent = 11*12), ferrous sulphate were mixed with 10 grammes 
('04 equivalent = 9*98) cupric sulphate. Only one crop was col- 
lected for analysis. 
V. Copper-Iron-Ammonium Sulphate. — This is a duplicate of 
IV. Only one crop was collected for analysis. 
VI. Copper - Cobalt - Potassium Sulphate. — 25 grammes 
( 1 equivalent = 24*95) copper sulphate were mixed with 28 grammes 
(*1 equivalent = 28*06) cobalt sulphate in presence of 35 grammes 
(*2 equivalents = 34*84) potassium sulphate. Three successive crops 
— Via, VI^, and Vly — were collected. The crystals of all the 
crops were rose-coloured. 
In the analytical separation of these samples some difficulties 
were experienced. When the copper was precipitated by means of 
sulphuretted hydrogen a re-precipitation was found to be absolutely 
necessary. Precipitation as cuprous sulphocyauate, by means of 
potassium sulphocyauate in presence of sulphurous acid, was found 
to work very well. To obtain perfectly accurate results, however, it 
is necessary to dissolve the precipitate in sulphuric acid, and to 
reprecipitate as sulphide. The precipitated sulphide was in all 
cases treated according to Rose’s method. The copper was also in 
some cases separated electrolytically. The first and second crops 
were kindly analysed for me by Messrs J. P. Macfarlan and Hugh 
Marshall, and the third crop by Mr Alexander Drysdale. 
VII. Copper - Magnesium - Potassium Sulphate. — This prepara- 
