AMOUNT OF ALCOHOL IN WINE. 149 



valueless. It is also necessary that this experi- 

 ment with wine should be made in a vessel of the same 

 shape and metal as that in which the thermometer was 

 graduated ; further, that the bulb of the thermometer 

 (ebullioscope) must be placed in the middle of the fluid, 

 and attention must likewise be paid to everything that 

 tends to promote equable boiling. 



One great difficulty here is how best to apply heat. 

 If it be irregularly conducted, now quickly and then 

 slowly, it would in the latter case cause relatively 

 more alcohol than water to evaporate before the liquid 

 boiled, and that is the moment for observation, and 

 the alcoholic contents of the wine would then be esti- 

 mated too low. A uniform source of heat, which will 

 cause the liquid to boil quickly, is therefore abso- 

 lutely necessary. 



That alcohol evaporates before the liquid boils is cer- 

 tain, and this occurs in the same manner in the experi- 

 ment which serves to graduate the thermometer, as 

 when the instrument is made use of to analyse wine. 



The points which I have endeavoured to investigate 

 are, first, whether the evaporation from alcohol before 

 the liquid boils, and when boiling begins, be as great 

 in wine as it is in alcohol and water; and secondly, 

 whether the solid constituents of wine do not so 

 modify the boiling temperature as to render the in- 

 strument inaccurate. It is scarcely necessary to re- 

 mind the reader that its applicability must depend 

 upon these details. 



