a ee 
J. Lawrence Smith on Emery. 365 
Another method by which I accomplished the levigation in ~ : 
some of the analyses, was in a steel mortar of the same formas 
the agate mortar; and when completed the powder was placed 
in a glass with nitric acid diluted with thirty times its weight of 
water and left in it for one hour agitating it occasionally. The 
iron taken from the mortar was. dissolved, and no part of the 
mineral attached. : The’ next thing was to filter and continue 
‘the analysis with the substance thus freed from the iron of the 
mortar,.without any second weighing. 
Of these two methods I preferréd to employ the first for the 
emery, a8 it is more expeditious and almost if not quite as exact 
as the second.-. There are, however, occasions in-which the steel 
mgstar should be resorted to. » eae 
The substance once reduced to an impalpable powder, it was 
necessary to render it completely soluble, and my researches to 
- afrive at.this were long and tedious. In trying the various known 
~ Methods the most successful was found to be that with a mix- 
- ture of carbonate of soda and caustic soda heated to whiteness _ 
for one hour; nevertheless I could not obtain a complete decom- . 
position, The decomposition might probably be completed if 
the levigation was made more thoroughly, but it is easy to. under- 
Stand, that with a large number of analyses of the same substance 
to make, it was a desideratum on my part not to consume the 
best part of a day in the levigation of a single gramme ; particu- 
, a8 I did not wish to confide this operation to another, as much 
Care was requir ose nothing during the levigation. Mixed 
with carbonate’@f baryta and heated in a forge, the decomposition 
of the mineral wagfar fronrbeing complete ; the same may be said 
: ISL Of potash. decomposes it almost entirely by a 
Single operation, but unfortunately, a double salt of potash and 
alumina is formed*which is almost insoluble in water or in the 
acids, and it is only by a solution of potash that it is first decom- 
posed and afterwards redissolved. I will not stop to detail all 
the disadvantages attending this method, but will at once speak 
of the method which gave me very easily the most accurate 
results. 
It is by means of the bisulphate of soda that all my analyses 
of emery, of corundum, and of several aluminates were made. 
I believe that I am the first who has shown the great advantage 
that I will say is, that the former in giving a decomposition at 
st as complete as the latter, furnishes a melted mass quite solu- 
