310 Br Baubeny 07i separating Lhne from Magnesia. 
Sclly, He took 30 grains of the Matlock calc-sinter, and added 
to it SO grains of carbonate of magnesia, both of which being 
dissolved in nitric acid, and treated with oxalate of ammonia, 
gave a precipitate which amounted to 51 gr. 
Now, as 30 : 51 : : 50 : 85. 
Wishing to confirm these results, Dr Kidd next took 50 
grains of calcareous-spar, and added to it 33.33 gr. of carbonate 
of magnesia, both of which were dissolved in nitric acid, and 
yielded with oxalate of ammonia 86.75. 
He dissolved 30 grains of the same calc-spar with 
20 grains of carbonate of magnesia, and obtained by the same 
re-agent, a precipitate which weighed 51 gr. 
Now, as 30 : 51 : : 50 : 85. 
I shall present the results indicated by these experiments in 
a tabular form, supposing the quantity of oxalate of lime formed 
from the pure carbonate, where no magnesia was present, to 
have been 100 grains, and reducing the others to the same 
ratio. 
Carbonate of Lime from lime-water, gave, 
^ — from the Matlock calc-sinter, 
Carbonate of Lime from calc-spar, 3 parts, ) 
Carbonate ®f Magnesia, 2 parts, i 
Carbonate of Lime from the Matlock calc-sinter, 3 parts 
Carbonate of Magnesia, - 2 parts 
Oxalate of Lime. 
100 gr. 
94.75 _ 
114.49 
’} 113.33 
■) 7 
The remarkable coincidence between these results, which, 
with the other particulars, 1 have been permitted to extract 
from the manuscript notes preserved by Dr Kidd, of a miscel- 
laneous set of experiments on various limestones, seems to esta- 
blish the general law, that when a large proportion of magnesia 
ispresentj^ in conjunction with lime, the precipitate thrown down 
by oxalate of ammonia exceeds by more than that which 
could be obtained by the same reagent from similar proportions 
of carbonate of lime, without any such admixture. 
Were we sure, indeed, that the increase was always in the 
ratio indicated by Dr Kidd’s experiments, our opinion as to 
the accuracy of the test might be less affected ; but as the ex- 
periments before t;elated lead to quite the opposite conclusion to 
this, it would be unsafe/ to trust to the oxalic test for the com- 
