SE eee Re 
Miscellanies. 189 
Hydrochlorate of soda — - . - - - 35 
0. ‘lime <a Ts ee 3 
Sulphate of magnesia - - - ie fom 10 
Do. im - - . - - 2 
Vegetable matter analogous to gelatine : - 8 
Loss and a little iodine ye As ah Aer a 7 
é —Idem. 
a. Charring of wood at low temperatures.—Mr. Charles May, 
chemist, of Ampthill, has sent me some specimens of wood converted 
into nearly perfect charcoal, at a very low but long continued heat. 
€ pieces, he informs, are part of the bottom of a tub, which held 
about 130 gallons, and which had been in use ih his laboratory about 
three years and a half, and almost constantly worked for boiling a 
weak solution of common salt, generally with an open steam pipe, 
and sometimes, though rarely, with a coil: the temperature was sel- 
dom higher than 216° or 220°, and the vessel was lined with tin roll- 
ed into sheets about one-sixteenth of an inch thick, and nailed to the 
inside; the joints, however, were not so good as to prevent the 
“liquid from getting between the metal and the wood. Mr. May states 
also, that he had long since remarked, that on making extracts with 
steam of very moderate pressure, all the apparent effects of burning 
might be produced, but that he was not prepared to find so complete 
4 carbonization of wood by steam; the vessel was made partly of fir, 
and partly of ash, the former of which was most perfectly reduced to 
1830 
& 
the state of charcoal. R. P.—Phil. Mag. and Ann. Nov. 5 
12. Limits to vaporization.—A paper on the above named subject, 
by Mr. Faraday, was published in the Philosophical Transactions for 
the year 1826: when the experiments therein mentioned were pub- 
“shed, others relating to the same subject were arranged, but which 
"equired great length of time for the development of their results. 
fler a lapse of four years the experiments were examined, and the 
Tesults are now stated. In September, 1826, several stoppered bot- 
Hes were made perfectly clean, and several wide tubes close at one 
*xtremity, so as to form smaller vessels, capable of being placed with- 
e the bottles, were prepared. Then selected substances were put 
‘ito the tubes, and solutions of other selected substances into the bot- 
tles; the tubes were placed in the bottles, so that nothing could pane 
from one substance to the other, except by way of evaporation. The 
Stopper S Were introduced, the bottles tied over carefully, and put away 
Na dark safe cupboard, where, except for an occasional examination, 
they have been left for nearly four years, during which time such 
