ELISHA MITCHELL SCIENTIFIC SOCIETY. 39 
ature between this and 350° C. He further states that a 
mixture of the salt and free acid, as prepared by him, 
when heated to this temperature until constant, yields 
the normal sulphate. It must be said that he gives no 
proofs of this bevond the amount of zirconia found in his 
atomic weight determinations. 
Whilst certain criticisms of the work of Bailey have 
occurred to me, I will refrain from mentioning them until 
I have had opportunity to repeat his experiments and so 
make myself more familiar with the details of his method. 
One criticism I can venture upon now, however. I 
doubt whether it is possible to ignite, without loss, zir- 
conia along with ammonium carbonate, as was done by 
Berzelius and by Bailey to remove the “‘last two or three 
milligrams of sulphuric acid.”’ I have not ventured to 
use this method in getting rid of the chlorine which is 
held just as tenaciously as the sulphuric acid. as I feel 
sure that it could net be done without loss. Bailey 
adopted extraordinary precautions to prevent this loss, 
but it seems to me that it is not the currents of the exter- 
nal atmosphere, as he maintains, which are to be most 
avoided, but the mass of escaping vapor of the ammonium 
salts. It is easily possible for him to have lost several 
milligrams of the finely-divided zirconia in this way, and 
as he states, each milligram was equivalent to a variation 
of 0.25 in the atomic weight. 
THE WEIGHINGS. 
In the following experiments the amounts of substance 
used varied from one to five grams. To avoid the disad- 
vantage of a small error causing a large variation in the 
result, I would gladly have used larger amounts of the 
chloride, but many difficulties met me there. The puri- 
fication of the zirconium oxychloride is slow and costly. It 
is best carried out in small portions of a few grams at a 
time. Some fifty grams have constituted the stock at my 
