On the Hydrometer. 23 1 



for fcveral reafons, to be the moft convenient. And as a 

 reference to it becomes neceflary, I have annexed this, 

 with the additional cohunns to it, by whicli the hydrometer 

 indications of ftrenglh are regularly deduced from the fpeciffe 

 gravity of the fpirit at this temperature*. 



In order to explain the manner in which I have calcu- 

 lated thefe additional columns, I conceive the eafieft mode 

 will be by an example. 



It being underllood bv the trade that the fpecific gravity 

 of proof I'pirit at this temperature (55) is.922, I looic at the 

 table for this fpecific aravity, and I fmd that it is a mixture 

 of pure fpirit and waTer, in the following pi-oportions, viz. 

 100 parts of the former to 81 of the latter (both by weight), 

 but that bv mcafure it is made by mixing 100 gallons of pure 

 fpirit with 66 gallons 99 parts of water. 1 then find that the 

 diminution of bulk, by penetration, on the mixture bv mea- 

 furc, (that bv weio-ht being unnecelTarv to attend to in bring- 

 ing out the refult,) is 4 gallons 57 parts, as, inrtead of pro- 

 ducing 166 gallons 99 parts, there will be only 162 gallons 

 42 parts. 1 find next, that this mixture contains per cent, cjf 

 pure fpirit 61 gallons 57 parts. 



Thefe being the proportions in the flandard of proof, to 

 which every other gradation of flrength is relative, the Rule 

 of Three demonlirates this relation in a manner recjuiring fo 

 be explained bv another example. Suppofe a ipirituous li- 

 quor is produced to afccrtain the hvdrometer indication ; on 

 weighing it in a phial adapted to this purpofe, I lind that at 

 the tc;nperaturc of 55, its fpecific gravity is 84H ; by looking 

 into the table \ perceive that this contains percent. 93*18 of 

 purefpiril. I then try how much morelhan proof this is by 

 iubtraiting 61-57 (the quantity wliich proof contains), and 

 I find that this has a redundance of pure Iplrit, amounting to 

 31-61. 



Therefore, as 100 gallons of pure fpirit require 66 gallons 

 99 parts of water to reduce it to proof, the redumlant 3f6r 

 will require 2\'i'j. Add thefe, and from the amount 5378 

 the diminution of bulk by |.enetration is to be dcduttcd, 

 which, by the ratio in proof fpirit being T44, the refult 

 fln.dlv comes out that this fpirit is 51 gallons and 34 parts 

 (about one-third) over hvdrometer pfoof. The under proofs 

 require lei's calculation, the excels of water per cent, over the 

 proportion which proof contains being all that is required. 



' It may |H.rli;ips lie ntccil'jry to obllrvc litre, iliat a rcftrence to tliis 

 mIjIc \i not rc<)aired in tliu uie of tlie liydiuiiicttT I have conllruflcd, 

 fuitlicr titan to iiy wliethcr it be corrciM. 



P4 Thife 



