ON MR. PATTINSON'S MAGNESIA ALBA. 
113 
ART. XXVI. — ON MR. PATTINSON'S MAGNESIA ALBA, AND 
ON THE COMPOSITION OF THAT SUBSTANCE GENE- 
RALLY. By George Fownes, Ph. D. 
Having been presented by Mr. Morson with a specimen 
of the magnesia alba, prepared by the new and very in- 
genious process of Mr. Pattinson, described at the last Phar- 
maceutical Meeting, I lay before the Society a short notice 
of the result of its examination. 
The color of the sample was beautifully white, and ft 
yielded, after calcination, perfectly white magnesia ; it was 
quite tasteless. When thrown into dilute hydrochloric or 
sulphuric acid, it dissolved with lively effervescence, the so- 
lution being quite complete, and the liquid free from turbid- 
ity. The solution, neutralized by ammonia, and mixed with 
oxalate of ammonia, remained quite unaffected, even after 
the lapse of many hours. The same solution mixed with 
excess of carbonate of ammonia, and warmed, underwent 
no change. Hence, I infer, the complete absence of lime. 
There is a minute trace of oxide of iron, but the quantity is 
exceedingly small and quite unimportant. 
The analysis of this compound was effected by the fol- 
lowing means : 
A weighed quantity was exposed to a full red heat for 
fifteen or twenty minutes, in a covered platinum crucible; 
the residue, found on examination to be pure magnesia, 
gave the quantity of that substance present. The carbonic 
acid was determined directly by decomposing a known 
weight of the preparation by excess of sulphuric acid, with 
the usual precautions. The water was estimated by dif- 
ference — 100 parts were found in this manner to contain, 
Magnesia, 41.6 
Carbonic Acid, .... 36.0 
Water, 22.4 
100. 
