B L O 



»nt(?nor Mu*. Tlie fubftance under examination being re- 

 <luced to the fize of a peppercorn, is to be placed in the platina 

 fpoon, Jig. 7. or into a fhallow cavity in a piece of conipaft 

 charcoal, and being firft gradually heated by the yellow 

 flame, g, is afterwards to be expofcd to the full intenfity of 

 the blue focus, h. 



An important ufe of the blow-pipe in the laboratory is to 

 foften glafs-tubes, &c. in order to bend them to any Ihape 

 that may be required, for which purpofe the blovT-pipe juft 

 defcribed is not very well qualified, tlie flame not being 

 [arge enough, and, from its intenfity at the blue fcrcus, 

 •fting very unequally. It may, therefore, in thefe, and 

 Cmilar cafes, be advantageouily fuperfedcd by the alcohol 

 blow-pipe. 



This inftrument, the invention of which is due, we beliere, 

 to M. Paul and profefTor Pidet of Geneva, has received fome 

 improvements from Englifii artills, and is figured in Chcmijiry, 

 P/dte'Kl. Jig. I. and 2. It is made of brafs, and confills of 

 the following parts : A is an oval bafe, in which are tv/o 

 round holes, for the reception of the two fpirit lamps, B, and 

 C, the latter of which has a conliderably thicker wick than 

 the former. D is a pillar that fcrcws into the bafe, and fup- 

 ports a moveable brafs collar, E, which may be retained at 

 any convenient height by the fcrew, F. L is the boiler 

 hanging loofely, but fecurely, in the collar, E ; M is a fcrew 

 accurately clofing an aperture in the boiler, through which 

 it is filled with alcohol ; I is a conical plug, ferving as a 

 fafety-valve, the refiftance of which to the expanfion of the 

 ▼apour is regulated by the fteel fprihg H, comprefTed be- 

 tween the fcrew nuts G and K ; O is the delivering pipe, 

 feen more particularly at Jg. 2. It confills of a plain tube, 

 «, fomewhat longer than the depth of tlie boiler, of a flioulder 

 »nd fcrew, b, by which it is fixed in the bottom of the boiler, 

 of a ball and focket joint (compofed of the Iphere, c, «', in- 

 clofing the perforated bulb and item e,JJ, and of the nut^, 

 terminated by a fmall aperture, &c. fcrewing on the ftem,y". 

 N {fig. I.) is a hollow cap, fcrewing into the boiler, and re- 

 ceiving the head of the tube, a, to prevent any liquid alcohol 

 from being thrown into it. This blow-pipe works in the 

 following manner : The boiler being filled with alcohol, and 

 the fcrews and valve fecured, the lamps, B and C, are lighted. 

 The alcohol in the boiler being brought to ebullition by the 

 lamp B, tlie vapour afcends into the cap N, whence it paffes 

 down the tube O, and is difcharged at P, upon the wick of 

 the lamp C, producing a long bulky horizontal flame Q, 

 •whofe extreme temperature is nearly equal to that of 

 melting copper, and is admirably fitted for the working of 

 glafs. 



Mr. Benjamin Hooke, lately an ingenious mathematical 

 inftrument-maker in Fleet Street, has made fome improve- 

 ments in the blow-pipe by alcohol ; for a defcription and 

 drawing of which we refer to Ni«holfon's Journal, vol. iv, 

 p. 106, 8vo. 



The blow-pipe is of confiderable ufe to^ the mineralogical 

 themiil, from its being very portable, and fliewing, in a few 

 minutes, upon a very fmall quantity of any mineral fubftance, 

 the effeft that would be produced by its cxpofure to the 

 heat of ourmoft powerful furnaces. It is alfo a valuable in- 

 ftrument in the analyfis of minerals, by indicating their prin- 

 cipal contents, rudely and iniperfeftly indeed, yet fo as 

 to afford a clue to the chemill in his fubfequent opei-a- 

 tions. 



The efficacy of the blow-pipe, in fufing the mod refraftory 

 fubftances, is, however, greatly increafcd by charging it with 

 oxygen gas ; a heat is thus produced, fully equal to that of 

 the folar rays concentrated by the belt Icnfes. The appa- 

 ratus for this purpgfe confills of the common blow-pipe, witk 



Vol.. IV. 



B L O 



th(* mouth-picce taken out, and conneflfd to a gatometo", 

 by a flexible tube of elaftic gum ; the curved tube and ter- 

 minating nut of the blow-pipe ought, however, to be made 

 of platina, the heat produced being fo intenfe as frequently 

 to fufe and inflame thofe parts of the inftrument, if made of 

 brafs. The operator fliould alfo be careful to wear fpeftack* 

 of green glafs, in order to proteft his eyes from the intolerable 

 white glow, which is fo intenfe as to caufe even the flame of 

 a common wax candle to caft a very fenfible fhade. Some- 

 times a double blow-pipe is made ufe of in experiments with 

 oxygen gas, by which the eflFeft is confiderably increafed. A 

 reprcfentation of this is feen in Chem'Jlry, Plate's.. Jg. ■^. 

 The part, a, which joins the tube of the gazometer, turns 

 air-tight in a collar, I, on the end of the tube, b, c. On thi« 

 tube aie two brafs boxes, d, e, into which are fitted the tubes, 

 J, g, which alfo turn in air-tight fockets, for the purpofe of 

 enabling the operator to move the blow-pipes, /i, i, nearer to 

 or further from each other. The blow-pipes, h, !, are alfo 

 moveable at /•, /, by which the direftion of the blafts may be 

 varied, fo as to meet on the charcoal, m, at any angle that 

 may be required. 



The caufe of the great heat vrhich is produced by the blow- 

 pipe, has generally been attributed both to a concentration 

 of the flame in a fmall focus, and a more rapid combuftion 

 than ufual. Count Rumford, however, (Effays, vol. ii. 

 p. 69.) fuppofes that the efFeft of this inftrument is entirely 

 due to the former of thefe caufes ; and in fupport of this hy- 

 pothefis, he mentions the refults of fome experiments made 

 by himftlf, which are fo contrary to daily experience, and 

 were conduced in fo inaccurate a manner, as to deferve, ia 

 our opinion, very little confidence. 



He begins by faying, " A current of air cannot generate 

 heat, without, at the fame time, being decompofed ; and, in 

 order to its being decompoftd in a fire, it muft be brought 

 into aftual contaft with the burning fuel, or at leaft with the 

 uninflamed inflammable vapour which rifes from it. But can 

 it be fuppofed that there can be any thing inflammable, and 

 not aftually inflamed,'in the clear, bright, and perfedlly tranf. 

 parent flame of a wax candle ? A blow-pipe has, however, 

 as fenfible an effetl when direfted againft the clear flame of « 

 wax candle, as when it is employed to increafe the aftion of 

 a common glafs-worker's lamp." To this it may be replied, 

 in the firft place, that flame is not tranfparent ; and, fecondly, 

 that a confiderable quantity of " uninflamed inflammable 

 matter" is contained in the flame, as is evident from the foot 

 that may be collefted by holding a plate of glafs or metal 

 over it, fo as juft to touch the fummit. The count proceed* 

 to relate that carbonic acid being driven by a blow-pipe 

 through the " clear, brilliant flame of a wax-candle juft 

 fnuff^ed," melted a fmall tube of glafs in the fame time at 

 when the pipe was charged with atmolpheric air, or even with 

 oxygen gas. We have repeated thefe experiments, and ob- 

 ferved, that when the blall was direfted to the whiteft part 

 of the flame, no well defined horizontal cone was produced 

 by any of the three gafes ; that when carbonic acid, or the 

 breath, was paffed through the flame juft above the wick, a 

 well defined cone was produced, the interior of which was of 

 a light blue, and the exterior of a pale yellow ; when atmo- 

 fpheric air was employed, the whole cone was of a bright 

 yellow ; and, with oxygen gas, the whole flame was of a 

 dazzling white. The cffeft of the fecond in melting glafa 

 was greater than that of the firft, and the laft was much more 

 powerful than the fecond. Neri, art de la Verrerie. Berg- 

 man's Eff. vol. ii. Philofophical Magazine, vol. viii. p. 325. 



BLOWER, fijujjhur, an appellation of contempt, foma- 

 times given to an alchemift. 



In the French king's kitchen, there was a,ncieutly an of- 

 4 M ficer 



