362 8S. L. Penfield—Deseloizite from Mexico. 
and were sent to Dr. Gibbs by Herbert G. Torrey, Esq., of the 
U. S. Assay office in New York. In all physical properties 
the mineral seemed identical with tritochorite recently described 
y A. Frenzel* from an unknown locality in either Mexico or 
South America. Whether identical with Frenzel’s mineral or 
not it was regarded as worthy of further investigation and Pro- 
fessor Gibbs kindly provided me with the material for analysis. 
Various methods of analysis were tried but the following was 
found to be the most satisfactory. The mineral was readily 
soluble in warm dilute nitric acid; to this solution enough sul- 
phuric acid was added to combine with the bases and the whole 
was evaporated till nitric acid was completely expelled; after 
cooling, cold water was added and after standing for some time 
the lead sulphate was filtered off and weighed with the usual 
precautions. The lead sulphate was soluble in ammonium ace- 
tate, except a slight residue of silica and a trace of vanadium, 
both of which were taken into account. No trace of vanadium 
went into solution in the ammonium acetate, so that the separa- 
tion was almost complete. To the filtrate from the lead sul- 
phate hydrochloric acid and sulphurous acid water were added 
and allowed to stand. The sulphurous acid was subsequently 
expelled by boiling and copper and arsenic precipitated by 
means of-hydrogen sulphide, filtered off and washed. After 
drying the sulphides of copper and arsenic they were transferred 
to a dry beaker and dissolved in nitric acid. The filter paper 
was treated in another glass with nitric acid and potassium 
chlorate to destroy organic matter. The solutions were then 
evaporated to dryness on a water bath, the residue dissolved in 
ter and the arsenic acid precipitated by means of magnesia 
mixture as ammonium magnesium arsenate. This was col- 
acid reaction this Prociieie dissolve 
ate and phosphate of iron; tliis latter was 
again ignited and weighed. It was then fused with sodium 
* Tschermak's Min. und Petr. Mittheilungen, iii, 506; iv, 97. 
