382 APPENDIX. 



quantities rotate the polarised ray in different degrees and 

 directions. Cane sugar rotates the light to the right ^ 

 and if treated with acid for a few minutes it is entirely 



changed into sugar which rotates to the left -< This is 



called uncrystallisahle sugar ; for if the solution be even 

 evaporated to dryness, it is changed into sugar which again 

 rotates to the right > . This sugar is called grape sugar 

 or glucose, and this sugar undergoes no change when again 

 treated with acid. 



By means of the saccharometer of Soleil, the degree of 

 rotation to the le^t or right can be measured, and thus the 

 quantity of sugar in a solution can be determined ; with cane 

 sugar alone the results are probably perfectly accurate. With 

 the other sugars the results are not yet so fully established : 

 still at least the minimum amount will be obtained. It is 

 essential that the fluids to be examined should be decolorised 

 first with one-tenth of a solution of subacetate of lead, and 

 afterwards, if requisite, with animal charcoal. 



Previous to the determination of the quantity of sugar 

 present in these liquids, when decolorised, they were examined 

 by other tests for sugar, by the sulphate of copper test, by 

 the liquor potassae test, and with the polariscope. I found no 

 Sherry, Port, Madeira, or Champagne that did not contain 

 more or less uncrystallisable sugar ; (two samples of sherry 

 excepted, which were free from any sugar.) I met with no 

 Claret, Burgundy, Rhine, or Moselle wine, (excepting only 

 one sample of Sauterne,) which was not free from every kind 

 of sugar. Usually spirits contain no sugar ; but one speci- 

 men of genuine French brandy had some cane sugar added 

 to it. All kinds of Ale, Porter, and Stout contain much 

 glucose. Hard cider I found also to be perfectly free from 

 sugar. Sweet cider contained uncrystallisable sugar. 



The particular results will be given in the Tables ; the 

 general results may be here stated. 



