352 REPORT—1846. 
The crystals of No. 5 are square prisms, having the angles truncated like 
No. 3. Hardness = 5°7. 
No. 1. Square prisms like No. 3. 
specific gravity of slag 
— 9, —O- 
Hardness = 6. At 19°2 C specific gravity of water =2°9052. 
No. 2. Square prisms like No. 3. 
f : 
Hardness = 6. At19°2C ~~ bel alt =2°9152. 
specific gravity of water 
Analysis——The slags composing the first series were found to contain 
silica, alumina, lime, magnesia, protoxides of manganese and iron, potass in 
small quantity, and sulphur as sulphuret. Phosphoric acid was also found 
in some of them. They are readily decomposed by digestion with dilute 
hydrochloric acid. The following method of analysis was adopted. 
Method of Analysis —1. The fine powder obtained by trituration in an 
agate mortar was digested with dilute hydrochloric acid. The whole was 
evaporated to dryness. The dry mass was treated with hydrochloric acid, 
and left fora few hours. Nitric acid was added sometimes before and some- 
times after evaporation to peroxidize the iron. The silica separated by fil- 
tration was washed with boiling water until nitrate of silver ceased to pro- 
duce the slightest turbidity, dried, incinerated at a bright red heat, cooled 
under a glass shade containing sulphuric acid, and then weighed. 
2. To the acid solution was added a slight excess of ammonia. Filtration 
was conducted as rapidly as possible, the funnel being covered with a glass 
plate. 
3. The precipitate (2) was boiled with potass. The solution was treated 
with an excess of hydrochloric acid, and the alumina then precipitated by 
carbonate of ammonia. 
4, The insoluble residue (3) was dissolved in hydrochloric acid, and the 
iron was precipitated by succinate of soda or ammonia with the usual pre- 
cautions. 
5. The lime was precipitated by oxalate of ammonia from solution (2), 
after treatment by ammonia. The precipitate, which consisted of oxalate of 
lime mixed with oxalate of manganese, was incinerated at a bright red heat, 
and then digested with dilute acetic acid, which dissolved the lime and left 
the brown oxide of manganese. A slight excess of sulphuric acid was added 
to the solution of acetate of lime; the whole was evaporated to dryness, and 
heated to redness; from the sulphate of lime thus obtained the lime was 
calculated. 
6. The solution (4), after separation of the iron, was added to solution (5) 
after separation of the lime. The manganese was precipitated by hydrosul- 
phate of ammonia in a close vessel, and in every instance at least twelve 
hours were allowed for precipitation. The sulphuret of manganese was dis- 
solved in hydrochloric acid, and precipitated as carbonate by carbonate of 
potass. The carbonate of manganese was incinerated at a bright red heat 
for a considerable time. The oxide of manganese thus produced was esti- 
mated as MnO-+ Mn? O3. 
7. The solution (6), after precipitation of the manganese, was digested 
with excess of hydrochloric acid until the sulphur separated by decomposi- 
tion of the excess of hydrosulphate of ammonia had completely separated. 
The magnesia was precipitated by phosphate of soda and excess of ammonia. 
Generally twenty-four or forty hours were allowed for complete precipita- 
tion. The precipitate was washed with ammonia-water until no sensible 
residue was left by evaporation on a plate of glass. When dry, generally 
as much of the magnesian salt as possible was detached from the filter, and 
