Tyro.
Dublin.
Footnote 3:[(return)]
"Speght, who states that a Mr. Buckley had seen a record of the Inner Temple to that effect."—Note by Sir H. N.
PHOTOGRAPHIC NOTES AND QUERIES.
Pyrogallic Acid (Vol. vi., p. 612.).—In answer to the Query of your correspondent E. S., I beg to give the following method of preparing pyrogallic acid (first published by Dr. Stenhouse), which I have tried and found perfectly successful.
Make a strong aqueous infusion of powdered galls; pour it off from the undissolved residue, and carefully evaporate to dryness by a gentle heat: towards the conclusion of the process the extract is very liable to burn; this is best prevented by continued stirring with a glass or porcelain spatula. Next, procure a flat-bottomed iron pan, about ten inches diameter and five inches deep. Make a hat of cartridge paper pasted together, about seven inches high, to slip over and accurately fit the top of the iron pan. Strew the bottom of the pan with the gall extract to the depth of three-quarters of an inch; over the top stretch and tie a piece of bibulous paper pierced with numerous pin-holes; over this place the hat, and tie it also tightly round the top of the pan.
The whole apparatus is now to be placed in a sand-bath, and heat cautiously applied. It is convenient to place a glass thermometer in the sand-bath as near the iron pan as possible. The heat is to be continued about an hour, and to be kept as near 420° Fah. as possible; on no account is it to exceed 450°. The vapour of the acid condenses in the hat, and the crystals are prevented from falling back into the pan by the bibulous paper diaphragm. When it is supposed that the whole of the acid is sublimed, the strings are to be untied, and the hat and diaphragm cautiously taken off together; the crystals will be found in considerable quantity, and should be removed into a stoppered bottle; they should be very brilliant and perfectly white; if there is any yellow tinge, the heat has been too great.
I believe that close attention to the above details will ensure success to any one who chooses to try the process, but at the same time I must remind your correspondents that scarcely any operation in chemistry is perfectly successful the first time of trial.