420 Dr. Stenhouse on some 
by dyers and leather-curriers, consists of the small branches 
of the Rhus coriaria. A quantity of sumach was digested with 
hot water, filtered and evaporated to dryness. The dried ex- 
tract thus obtained was subjected to distillation. The liquid 
which passed into the receiver, though it gave no crystals of 
pyrogallic acid, obviously contained that substance, as it ex- 
hibited all its characteristic reactions. The pyrogallic acid 
was prevented from crystallizing by the empyreumatic oil and 
other impurities by which it was accompanied. It seemed 
not improbable, therefore, that sumach contained gallic 
acid, and that perhaps its tannin was also similar to that of 
alls. 
a The first step taken, therefore, was to examine sumach for 
gallic. Several pounds of sumach were repeatedly boiled with 
water and then filtered. The tannin contained in the liquid 
was precipitated by solution of glue and separated by filtra- 
tion. Its quantity was very considerable. The clear liquid 
was evaporated to the consistence of an extract, and treated 
with hot alcohol. The greater portion of the spirits was re- 
covered by distillation, and the residue set aside to crystallize. 
After some days, as no crystals made their appearance, the 
alcoholic solution was evaporated to dryness on the water- 
bath. It was then introduced into a stoppered bottle and re- 
peatedly agitated with ether; almost the whole of the zether 
was distilled off, and the residue left to spontaneous evapora- 
tion. Abundance of reddish coloured crystals soon appeared. 
They were purified by repeated digestions with animal char- 
coal and successive crystallizations. The crystals were then 
perfectly colourless and possessed the silky lustre of gallic 
acid, with which acid their reactions with salts of iron and 
other reagents completely corresponded. When distilled 
they yielded abundance of pyrogallic acid. They were dried 
at 212° F, and subjected to analysis. 
I. 0:2932 gramme substance gave 0'5315 carbonic acid, and 
0°963 water. 
II. 0°2824 gave 0°508 carbonic acid, and 0°956 water. 
I. II. Calculated. 
C 50°12 49°73 “C = 49°89 
H 3°64 3°76 3H= 3:49 
O 46°24 46°51 5 O = 46°62 
100°00 100:00 100:00 
These results approach pretty closely the calculated num- 
bers of hydrated gallic acid given above. 
In order to determine the atomic weight of the acid, the 
basic gallate of lead was formed by adding a solution of the 
