41090 GEOLOGY OF OHIO. 
up for Escha’s method with magnesia, using Dr. Drown’s modifica- 
tion. 
2nd. This method avoids the excessive wear of the platinum 
crucibles which the ordinary method occasions, gives results fully as 
accurate, and also avoids the presence of such an excess of saline com- 
pounds in the solution in which the baric sulphate is precipitated. 
Before adopting it, a large number of duplicate determinations by 
both methods were run through with satisfactory results ; in a few cases, 
where notable differences resulted, the Escha method gave the higher 
results, and considering the great liability to loss while deflagrating 
the sodic nitrate and coal mixture, the error certainly seemed explained 
thus. 
The Escha method, as we used it, was as follows: One gramme of 
coal or coke was well mixed with one and a half grammes of a mixture 
of one-third pure, dry, carbonate of soda, and two-thirds dry, pure, 
ignited magnesia. | 
The light mixture was transferred to a platinum crucible of about 
30 c. c. capacity, which was then heated very slowly and gradually 
over a Bunsen burner, the crucible being tilted on its side, and the flame 
turned so low that all generation of gas in the crucible was avoided ; 
the mixture yradually and quietly burns white. When so burned 
(which takes from 45 minutes to an hour) the mixture, which does not 
fuse, but remains as a powder, is transferred to a beaker, water added, 
digested warm for a few minutes, filtered, and the residue washed. To 
the filtrate was added a little bromine water, the excess of which was 
expelled by heat, and the sulphuric acid precipitated with baric chloride. 
In all sulphur determinations it was found impossible to obtain 
reagents free from sulphur. The nitrate and carbonate mixture used 
in the first method was made in considerable quantities at a time, mixed 
well, and the sulphur it contained accurately determined ; this was then, 
in all cases, deducted from that found in the coals. The amounts thus 
found in “chemically pure” sodic carbonate was in some cases equivalent 
to 3% to 33, of a per cent. on the gramme of coal. 
The same difficulty was encountered in preparing magnesia for the 
Escha method; “ chemically pure”? magnesia yielded sulphur so abun- 
dantly that it was discarded, and the following method adopted for obtain- 
ing better: good commercial magnesia was boiled with sodic carbonate, 
then washed by decantation until the liquid, acidified by hydrochloric 
acid, ceased to yield a precipitate with baric chloride. The magnesia 
