398 Foreign and Miscellaneous Intelligence. 



but long-continued heat. The pieces, he informs me, 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, gene- 

 rally with an open steam-pipe, and sometimes, though rarely, with a 

 coil : the temperature was seldom higher than 216 or 220/and the 

 vessel was lined with tin, rolled into sheets, about the 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*. 



29. CHANGE OF COLOUR IN THE WOOD OF CERTAIN TREES. 



M. Marcet has experimented upon this point, particularly with the wood 

 of the alder, which, exposed to air, becomes red or brown. The 

 change did not take place if, the instant the wood was cut, it was 

 introduced into a perfect vacuum, or into gases containing no oxygen ; 

 but, on the contrary, being put into oxygen, the red colour became 

 more vivid than in the air. If the wood, when cut, was plunged 

 into water, it always reddened, whatever attempts were made to 

 exclude oxygen. Some of the wood, which had acquired a yellow 

 colour, communicated that colour to water, and the water, being 

 evaporated, left a substance having every character of pure tannin. 

 M. Marcet concludes, from his experiments, that the colouration of 

 the alder wood is always due to a degree of oxygenation which 

 the tannin undergoes immediately upon its exposure to the air or 

 oxygenf. 



30. PRESERVATION OF BLOOD. 



Sugar refiners and others are often inconvenienced by the difficulty 

 of obtaining blood at the time when it is required for use. M. Toursel 

 has endeavoured, in part, to remove this difficulty, by proposing a 

 method of preserving this agent for some time without injury. It 

 consists in putting the blood into bottles or other vessels with very 

 narrow mouths, and being careful to fill them up to the neck ; a layer 

 of oil, to the depth of at least half an inch, is then put upon it to cut 

 off communication with the atmosphere, and the whole is left to 

 itself. M. Toursel states that he has in this manner preserved blood, 

 \yith all its physical and chemical qualities, from the 1st of December, 

 1827, to January, 1829J. 



* Phil. Mag. N.S. viii. p. 383. f Bib. UmV, 1830, p. 228. 



:j: Journ. do Commerce. 



