33° Experiments on the j4Jhes 



oxygen ; and thofe which depend on the Irate of concentra- 

 tion pofielled by oxygen, conltitute the leading caufe of thofc 

 phenomena which arife from the changes of combination in 

 daluc fubftances. (Art. XIV. Nos. t% and 15.) 



[ To be continued. ] 



LI. Experiments on the Aflies of fome Kinds oj Wood by 

 C. Pis sis, Phxjidan at Brionde 3 in the Department of 

 la Haute Loire*, 



H 



.AVING burnt, during the winter of the year 8, a 



treat deal of poplar as lire-wood, I remarked that the allies 

 V being re- burnt on the hearth, formed cruris of real frit, 

 fuch as that of the allies of fea-wced, with this difference, 

 that they were only thin and of little extent, having neither 

 been ilirred, nor received any other heat than that of a mo- 

 derate fire ufed in a parlour. I firlt fufpecled I had obtained 

 an extraordinary quantity of potafib ; but as 1 durft not ven- 

 ture to afcribe it to the quality of the wood, as the white kinds 

 of wood have always been confidercd as furnifhing little fa- 

 line matter, the trembling poplar (Populus tremula, Linn.) 

 a tree of the fame kind as our common poplar (Populus alba) 

 turniil.ing only, when burnt with the greateft care, 9 drams, 

 45 grain?, of potafh per quintal of wood, I imagined that 

 it depended on an alteration in the ligneous body. We culti- 

 vate the poplar for the purpofe of obtaining props for our 

 vines, and as it is bad fire-wood, we never cut it till it ceafes 

 to throw forth (hoots. It is not uncommon to fee poplars 

 having the bark and branches exceedingly vivacious, while 

 thejtrunk is reduced to a few handfuls of vegetable mould. 



This idea of the augmentation of potafh in rotten wood 

 was not perfectly correct, but it will be feen that it conduc- 

 ted me to refults very different from the opinions commonly 

 received. But I fhal! return tothefe theoretic points when I 

 have detailed the following experiments, which will ferve to 

 illuftrate them. 



ift, A hundred parts of dry and found poplar wood pro- 

 duced four parts of allies. 



sd, A hundred parts of dry and rotten poplar wood, but 

 not yet in the ftate of mould, produced eight parts of allies. 



3d, A hundred parts of each of thefe kinds of allies, lixivi- 

 ated till the water became infipid, and completely dried on 



* From the Anualcs dc Cbimie y No. 112, 



