Defcripikn of a Three-llafi Fufing Vurnace. 69 



alfo an acid, which muft necefTarily have a greater or lefs ac- 

 tion on the extraftlve matter of the vegetables, change its 

 nature, and incrcafe in the extrads the tendency they have 

 to deliquefcence. 



l6lh. Vinegar extrafts very badly the principles of vege- 

 tables ; it generally alters them, or is altered by them. 



It may however be ftill employed as a folvent in regard to 

 fquills, garlic, refinousgums, and as a vehicle of the odonrs 

 ^nd colours of fome flowers. 



17th. Extrafts by highly reftified alcohol are refins ; by 

 weak alcohol they are refins mixed with gummy or extractive 

 fubftances. 



Vegetable fabfl:ances fubjciled to the a6lion of alcohol are 

 dry, and much divided: this adtion is affiCted by a degree of 

 heat more or lefs confiderable. The velTel in which the ope- 

 ration is performed muft be fufficiently large to allovv the 

 vapours to circulate. 



When the folution has been made and filtered, water is 

 poured over it, and the alcohol abandons the refill to unite 

 with the water; or it is fubjefted to didillation, and the 

 alcohol paflfes off in vapours, leaving the refin free in the 

 fame manner. 



i8th. If jalap, for example, has been employed, to obtain 

 the refin, and if it be intended to procure the gummv ex- 

 tra6l of this root, the exhaufied refiduum of the refin nuift 

 be treated with water, after which the infufion is filtered and 

 evaporated. 



It refults from thcfe general confiderations on vegeta- 

 ble extrafts, that the pharmacopolift, if he proceeds me- 

 thodically, vvill always have the fatisfaftion of furnifliing the 

 healing art with medicines containing the whole of the im- 

 mediate products of vegetables, and confequeiuly fufceplible 

 of producing the effefts which effentially belong to them. 



XII. Dcfcription of a Three-hlajl Fufing Fun/ace, coiiJlruScd 

 in the Chemical Lab')ratory of the French School of Mines. 

 By P. To RE LL I -N ARC I, attached to the Council of 

 Mines. 



A HIS furnace is deftined for fufin<^ din'cix'nt mineral 

 fubftances, in order to afcertain the nature of thcin ; and the 

 experience of fix years has (hown that itanfwcrs the intendid 

 purpofe. By its means a very intenie heal is oblaiued, and 

 il was employed by C. Clouct lor repeating his experiments 



