Experiments tuith the Lamp Furnace. tit 



itis unneceffary to Tpeak morelargely of itinthis place*. Nothing more was required but to 

 adapt it to the fqnare iron ftem which paffes through the refervoir of the lamp. The connec- 

 tion is made by apitce of wood, in order that lefs of the heat might be difperfed. As the lantp 

 itfelf is capable of being moved x>n its ftem, it is eafy to bring it nearer or remove it at 

 pleafure from the veflsls, which remain fixed; a circumftance which, independent of the ele- 

 vation or deprellion of the wick, affords the means of heating the retorts by degrees, of 

 moderating or fuppreffing the fire inftantly, or of maintaining it for fevera! hours at a con- 

 ftant or determinate inienfity, from the alniolt infenfiblc evaporation of cryftallizable folu- 

 tions to the ebullition of acids ; properties never poflefled by the athanor, of which chemifts 

 have boafted fo much. The advantage of thefe will be properly valued by thofe operators, 

 who know that the moft experienced and the moll attentive chemifts meet with frequent ac- 

 cidents, by which both their vefiels and the products of their operations are loft, for want of 

 power in the management of the fire. 



I muft here enter into fome detail, in order to eftablifli upon pofitive fads the poflibility 

 of applying the heat of a lamp to the operations I have enumerated, as well as to communi- 

 cate the refults of my experience to thofe who in preference, or for want of more extenfive 

 means, may be inclined to life this apparatus. I do not hefitate to fay in preference ; for, in 

 the beft appointed laboratory, the lamp will alfo be ufed in fuch operations as may be made 

 with equal facility on the fame quantities, in much lefs time and more conveniently than by 

 the fire of a furnace, by burning in the former inftancc one or two decimes (or penny- 

 worths) of oil inftead of five or fix decimes of charcoal. The proof of this has been made 

 in the laboratory of the Polytechnic School, at the conclufion of my laft courfe. 



For the analyfis of ftones, fuch as the cryftals of tin, on which I operated before the clafs 

 at the feflion of the firft Mcflidor laft, I ufe the ftiortened chimney of glafs. I begin by 

 placing the mixture in a capfule of platina or filver of feven centimetres (2-^ inches Englifti) 

 in diameter. I place this capfule on the fupport, and regulate the heat in fuch a manner 

 that ebullition ftiall take place without throwing any portion of the matter out of the veflel. 

 As foon as its contents are perfectly dry, I transfer them into a very thin crucible of 

 platina, of which the weight is not quite eleven grammes (25 2 i^ grains Englifti), and its 

 diameter forty-five millimetres (i|- inch Englifti'). This crucible refts on a fmalj fupport 

 •of iron- wire, which ferves to contract the ring ; and the wick being at its grcateft elevation, 

 with the ring lowered to the diftance of twenty-five millimetres (p^- inches Englifti) from 

 the upper rim of the glafs chimney, I produce in lefs than twenty minutes the faline fufion 

 to fuch a degree, that from the commencement of the operation the decompofition proceeds 

 as far as to 0,70 of the mineral f. 



The fame apparatus, that is to fay, with the ftiortened chimney, ferves for oxidations, in- 

 cinerations, torrefa£lions, and diftillations todrynefs. 



In fuch operations as require a lefs heat, I leave the lamp with its large chimney abfolute- . 

 \y in the fame ftate as when it is ufed for illumination ; and by raifing and lowering either 



• SeTeral philofophers who have fcen this apparatus at work, having requefted me to give a drawing, I have 

 accordingly annexed a defcription of the figures, which rcprefent the whole together at the end of this memoir. 

 I think it may be called the Economical Laboratory. 



f See the Annales de Chimie, xxiv. 132 ; or our Journal, I. 545, 



E e 2 the 



