FROM INEQUALITY OF HEAT IN LARGE DISTILLATION. ]57 



2nd. If the fire be differed to flacken too much, theconden- Low heat caufes 

 fation produces a vacuum in the worm and the alembic, which e n t e ° Ut ^ n * ,r _ t(> 

 not being fupplied in the fame proportion by frefh fleam, oc- when expelled 

 cations the outer air to enter, which renders the evaporation carries ou t va- 

 and condenfation more difficult, and when it is, at laft, driven 

 out, it takes with it a portion of the fleam, thus occafioning a 

 lofs of the matter under diftillation, as well as a lofs of time. 



In order to remedy thefe defects, and at the fame time to Inftruments for 

 furnifh a fimple method of regiflering the adual heat, I have ^^ ying thefc 

 thought of the following inflrument, which is applicable to 

 any diftilling apparatus, and is nothing more than an applica- 

 tion of known principles of theory to actual practice. 



a, b, c, d, Fig. 1. is a bent tube of copper or glafs in fe- An inverted 

 parate pieces, with a bulb at b; the upper end of the tube a { J ph ™ ° f . con " 



i . , , l r ~ , denfed fluid, and 



may be attached to the worm by means or a lcrew. The length a mercurial gage 



b c, c d is of four feet, and the capacity of the bulb b, is a little which a,, °w3 of 

 larger than the whole capacity of the tube be d. The diftillation internal or ex- 

 being begun, the condenfed fleam will pais by a and the bulb te . rnal preiTure, 



b, into the tube bed; and when its two arms are full, the li- „,, ?" • con ?' 



' * ^ municdcion from 



quor will run out at d, into the veftel J n tended to receive it. without. 

 Thefe two arms, therefore, remain full during the whole of 

 the diftillation, and in this confifts the remedy to the inconve- 

 nience above-mentioned ; it is evident that if the fire becomes 

 too quick, the uncondenfed fleam cannot force a paflageto the 

 outer air, in order to diffipate itfelf, till it has driven out all 

 the liquor contained in the tube b c, and has overcome the 

 preftlire of a column equal in height to c d. Again, the outer 

 air cannot enter to fill up the vacuum produced by the flow- 

 nefs of the fire, but by driving back the column dc, and 

 overcoming the prefture of the fame height. Now this co- 

 lumn being four feet, gives range and time fufficient for the 

 operator to regulate the fire accordingly. If the tube bed 

 were made of glafs, we fhould only have to obferve the level 

 of the liquor in the two arms, the fall in b c would indicate 

 that the heat Ihould be diminiflied, and in c d, that it (hould 

 be increafed: but tubes of this length being fubject to acci- 

 dents, I prefer attaching to c a fmall regulator of glafs, e f e, 

 the two arms of which, e f, each of three inches long, con- 

 tain mercury, and which rifing in them alternately, will indicate 

 the flate of the heat and ihe fleam with fufficient accuracy. 

 This regulator may be placed in a bottle or flafk, which will 



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