18 CONTRIBUTIONS TO MINERALOGY. [bull. 262. 
CHEMICAL ANALYSES AND DISCUSSION. 
By W. F. HlLLEBRAND. 
I. GREEN COLORING CONSTITUENT OF PLACERVILLE SANDSTONE. 
As noted by Doctor Ransome, the greener the sandstone the greater 
has been the replacement of the calcareous cementing material by the 
crystalline vanadiferous mineral. Fortunately, the greenest available 
specimen was entirely free from carbonate, and this was used for] 
analysis, 10 grams being taken for the main portion. 
The green substance was but slightly attacked by cold acids and not 
rapidly by hot ones, nevertheless after from twelve to twenty-four] 
hours' digestion on the water bath with diluted nitric acid the greenish] 
color had been transferred to the liquid, the residue of sand was nearly] 
white, and a rather voluminous separation of nongelatinous silica had 
taken place. The filtration and washing of the insoluble matter was! 
accomplished without difficulty. The free silica in it was extracted by] 
two or three digestions of fifteen minutes each on the water bath with! 
sodium carbonate solution of 5 per cent strength. The flocculent matter} 
had entirely disappeared and the sandy residue was collected in a Goochj 
crucible and washed with hot sodium carbonate solution, followed bfl 
very dilute nitric acid, and finally by alcohol, to prevent turbid filtra- 
tion. Drying of the sand was effected b} r allowing the pump to draw ' 
air through the crucible until no further loss in weight resulted. 
The water in the sand was then determined at 105°, at 300 , and 
above 300°. Similar water determinations having been made on the|« 
unattacked substance, the differences gave the water expelled at those 
temperatures from the soluble part. 
The sodium carbonate solution was acidified, evaporated, and fil- 
tered, and the filtrate again evaporated, to recover the last of the silica. 
To this was added a very small portion which the nitric-acid extract 
of the sandstone held in solution. The sum represents the total silica ij 
of the decomposed portion of the sandstone. 
The further analysis of the nitric solution presented difficulty 
because of the vanadium it contained. It was carried out in a variety | 
of ways, of which the following seemed to be most satisfactory: 
Barium was first precipitated by sulphuric acid and subsequently 
separated from traces of lead, calcium, and vanadium. Hydrogen 
sulphide then threw out further traces of lead and copper with much i 
sulphur from reduction of V 2 O s to V 2 4 . After evaporation of the j 
filtrate to reoxidize vanadium and iron, the alumina, iron, and trace 
of uranium with much vanadium were separted from the calcium, j 
magnesium, and alkalies by three precipitations by ammonia solution. ! 
The combined filtrates were evaporated and ignited, the residue was 
transferred to a porcelain boat with nitric acid, evaporated therein to j 
complete dryness, and exposed in a glass tube to a current of dry 
