Miscellanies. 189 



Hydrochlorate of soda ~ . . ^ ■. 35 



Do. lime ----- 3 



Sulphate of magnesia - - - - ^ 10 



Do. lime - - - - - - 2 



Vegetable matter analogous to gelatine - - 8 



Loss and a little iodine ^ - - .- - 7 



— Idem. 



11. 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. 

 The pieces, he informs, are part of the bottom of a tub, which held 

 about 130 gallons, and which had been in use in 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 

 a 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 

 the state of charcoal. R. P. — Phil. Mag: and Ann. Nov. 1830. 



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- 

 lished, others relating to the same subject were arranged, but which 

 required great length of time for the development of their results. 

 After a lapse of four years the experiments were examined, and the 

 results are now stated. In September, 1826, several stoppered bot- 

 tles were made perfectly clean, and several wide tubes close at one 

 extremity, so as to form smaller vessels, capable of being placed with- 

 in the bottles, were prepared. Then selected substances were put 

 into the tubes, and solutions of other selected substances into the bot- 

 tles ; the tubes were placed in the bottles, so that nothing could pass 

 from one substance to the other, except by way of evaporation. The 

 stoppers were introduced, the bottles tied over carefully, and put away 

 in a dark safe cupboard, where, except for an occasional examination, 

 they have been left for nearly four years, during which time such 



