of fome Khuh of Wood. 33* 



*n ignited plate of iron, loft 28 parts in weight: the firft 

 waters were very ftrong. 



4th, A hundred parts of the fame allies re- burnt and 

 treated as above loft onlv 22 parts: the leys were ftronger 

 and more caullic than the preceding. 



5th, A hundred parts of the afhes of dry and found oak,- 

 re-burnt and treated as above, loft 16 parts. 



6th, A hundred parts of moift mould of oak of an ochre 

 colour, placed on an ignited plate of iron, became dried and 

 incinerated very fpeedilv, and left three parts of afhes, which, 

 though re-burnt, had the colour of iron filings. Tins is 

 nearly the double of what a quintal of dry oak gave when 

 burnt with the greatell care. Thefe afhes were perfectly 

 in lipid. 



7th, A hundred parts of the frit mentioned in the begin- 

 ning of this paper, treated in the fame manner as the afhes 

 of No. 3, loii 37 parts in weight. This frit appeared at firft 

 to be infip'd ; the potalh was concealed in it, but, by length 

 of time and trituration, the water carried off a great part of 

 it; yet it is probable that there remained fome of it in the 

 reficluum by means of a fort of vitrification. Thefe leys were 

 very cauftic. 



8th, Some morfe]s of this frit brought to a red heat in the 

 fire, and quenched in a fmall quantity of water, furnifhed a 

 ley fo cauftic as to convert into foap melted wax and tallow,, 

 on which the lev was poured cold. 



9th, This ley filtered on baked plafter of Paris (fulphate of 

 lime mixed with lime) reduced to powder, loft its alkaline 

 tafte, and furnifhed by fpontaneous evaporation beautiful 

 crvftals of fulphate of potafh. 



It follows from thefe experiments : 



i ft, From the four firft compared with the fifth, that the 

 wood of the white poplar is richer in faline matter than oak : 

 here then we have an exception to an admitted rule, which 

 confiders hard wood as the moft abundant in potafh. Hie 

 poplar is a wood fo fpongy that rats cannot pierce it ; the 

 filaments of it rcfitt their teeth in the fame maimer as hemp 

 would do ; it is difficult to be fawn, and is exceedingly fub- 

 ject to rot : in order to be eafily fawn it muft be cut when in 

 its vigour, which is never thought of, as I have already faid. 

 This wood when dry burns with a white flame, gives little 

 heat, is fpeedily confumed, and makes no cinders. It is 

 evident that it abounds more with mcombuftiblc parts than 

 qther kinds of wood ; which is the cafe alfo with the willow, 

 which gives. a quantity of afhes twice as great, but only about 

 as much faline matter^ as the oak ; tjut 1$ to fay, 15 grammes 



(2310 



