DOLOMITE AND MAGNESITE WITH REFERENCE TO THE SEPAR- 
ATION OP CALCIUM AND MAGNESIUM. 
BY InICIIOLAS knight AND WARD II. WHEELER. 
The estimation of calcium and magnesium in a mineral or rock is 
frequently necessary and seems like a simple matter, yet a great deal of 
work has been done on the subject, and different views are held as to the 
best procedure. The method that he has become accustomed to is 
doubtless the best for the individual analyst or teacher. Some of the 
.methods, however, seem to be more simple and direct, and therefore 
less likely to lead to error than other processes which have been devised. 
^Richards developed a method for the separation of calcium and 
magnesium where the substances are somewhat equal in amount, as in 
dolomite, and his method differs in some important particulars from 
those commonly employed. 
To the solution of calcium and magnesium chlorides, Richards adds 
three grams of ammonium chloride, then oxalic acid and sufficient 
hydrochloric acid to keep the calcium in solution. A drop of methyl 
orange solution is next added as an indicator, and dilute ammonia 
slowly, with constant stirring to alkaline reaction. Lastly an excess of 
, ammonium oxalate is added. 
In applying this method, we found some difficulty in getting all the 
magnesium precipitated. Indeed four successive crops were obtained. 
This was doubtless due to the large amount of ammonium oxalate 
employed. One advantage claimed for it is the small amount of mag- 
nesium precipitated with the calcium, which in two determinations was: 
1. .0011 Mg 0 equivalent to .42 per cent of the whole. 
2. .0013 Mg O equivalent to .54 per cent of the whole. 
Average .48 per cent of the whole. 
In our experiment with this method we obtained .0028 Mg O equiva- 
lent to 1.24 per cent of the whole. 
By wdiat seems to us a simpler method, which will be explained later 
w^e found only .08 per cent MgO equivalent to .37 per cent of the whole, 
and in a number of instances we obtained .11 per cent MgO equivalent 
to .51 per cent of the whole. 
We afterwards repeated the experiment and obtained .13 per cent. 
On re-dissolving this and re-precipitating we found only .01 per cent. A 
second time we obtained only .07 per cent, which when re-dissolved and 
re-precipitated gave no residue, and a third time we found no magnesium 
had precipitated. 
*Zeitsclirift fur Anorg. Cliemie July, 1901. 
