DESCRIPTION OF ATKINs's HYDROMETER. 277 



ever, remains to be done in order to the eflimation of the Correftlons ne- 



' „ r r ceiiary to be ap- 



tfrengths of fpirtuous liquors: the contradion ot the mals ot a plied 

 compound of alcohol and water on their mixture, and the va- for concentration 



. ... ,. «» i rand temperature. 



nation in its meaiure in refpecl of temperature, are each ot 

 them of fufficient practical importance to render their apprecia- 

 tion neceffary when the value of the fpirit is to be difcovered. 

 Thus for example, 18 gallons each of alcohol and water will a fj a a ^Ter ° f 

 produce only 35 gallons of the compound, and a difference of produce only 35 

 30° in temperature of Fahrenheit's fcale, occafions fuch a °/ the mixtur f* 



r . . c . 1 A variation or 



change in the fpecific gravity of proof fpirit, as, if omitted to 30 of temp, oc 

 be taken into consideration, would render the dealer liable to cafions a change 

 an error of upwards of ten per cent, in the efiimation of its in t ^ e app rren j 

 ftrength and confequent value. ftrength of 



In commercial tranfa&ions withrefped tofpirituous liquors, Commercial eMr 

 it is neceffary to appreciate their ftrength by comparing it with mation of value 

 that of fpirit of a certain fuppofed quality in this refpeft as a ^'^J"* 

 ftandard. This ftandard-fpirit (which is called proof-fpirit) is 

 of fuch a degree of ftrength that its fpecific gravity is about 

 .920 at 60° of Fahrenheit's thermometer ; and the object of 

 enquiry in all cafes is with regard to the quantity of this proof h l companfon 

 fpirit which would be equivalent to a given quantity of any fpirit. 

 fpirit under examination. The language of the fpirit-dealers Definition of 

 with refpect to their terms of ** over-proof" and " under-proof" (i pr00 p ■ an( j 

 has in all cafes this kind of reference to commercial value. " under-proof.'* 

 When they fay that a certain kind of fpirit is 30 per cent, over 

 proof, they mean that if 100 parts by meafure be increafed to 

 130 by the addition of water, it will become of proof ftrength ; 

 and when they fay that it is 30 per cent, under proof, they 

 mean that 70 parts by meafure of proof-fpirit will become, 

 when increafed to 100 by the addition of water, of equal 

 ftrength to that of the fpirit in queftion. If therefore a gallon of 

 proof fpirit be worth 8s. 4-d. the fame quantity of the former 

 kind of fpirit will be worth 10s. lOd. and of the latter 5s. lOd. 



It is not therefore fufficient for the purchafer of a fample of 

 fpirit, or the officer who is to collect the duties on it, to be in- 

 formed of its fpecific gravity at a given temperature : it is ne- The defideratum 

 ceffary for him to afcertain the quantity of proof-fpirit which is Is ^lelt^uan- 

 capable of producing, or being produced, by the fpirit in queftion tity of proof- 

 by the addition of water only, and which is confequently equi- *P irit * 

 valent to it in value. 



The 



