XVI] WINES 237 



From IX, 9, ascertain the per cent by weight of extract in the dealcoholized wine 

 corresponding to the value of S. Multiply the figure thus obtained by the value of 

 S to obtain the grams of extract per 100 cc. of wine. 



12 By Evaporation.— Tentative. 



(a) In dry wines, having an extract content oj less than 3 grams per 100 cc. — Evapo- 

 rate 50 cc. of the sample on a water bath to a sirupy consistency in a 75 cc. flat- 

 bottomed platinum dish, approximately 85 mm. in diameter. Heat the residue 

 for 2^ hours in a drying oven at the temperature of boiling water, cool in a desicca- 

 tor and weigh as soon as the dish and contents reach room temperature. 



(b) In sweet xvines. — When the extract content is between 3 and 6 grams per 100 cc, 

 treat 25 cc. of the sample as directed under (a). 



When the extract exceeds 6 grams per 100 cc, however, the result, obtained as 

 directed under 11, is accepted and no gravimetric determination is attempted. 

 This is because of the serious error connected with drying levulose at high tempera- 

 ture. 



13 NON-SUGAR SOLIDS.— TENTATIVE. 



Determine the non-sugar solids (sugar-free extract) by subtracting the amount 

 of reducing sugars before inversion, 14, from the extract, 11 or 12. If sucrose is 

 present in the wine, determine the non-sugar solids by subtracting the sum of re- 

 ducing sugars before inversion and the sucrose from the extract. 



14 REDUCING SUGARS.-TENTATIVE. 



(a) Dry wines. — Place 200 cc. of the wine in a porcelain dish, exactly neutralize 

 with N/1 sodium hydroxid, calculating the amount required from the determina- 

 tion of acidity, 25, and evaporate to about one fourth the original volume. Trans- 

 fer to a 200 cc. flask, add sufficient neutral lead acetate solution to clarify, dilute 

 to the mark with water, shake and filter through a folded filter. Remove the lead 

 with dry potassium oxalate and determine reducing sugars as directed under VIII, 



25. 



(b) Sweet wines. — In the case of sweet wines approximate the sugar content 

 by subtracting 2 from the result in the determination of the extract and employ 

 such a quantity of the sample that the aliquot taken for the copper reduction shall 

 not exceed 245 mg. of invert sugar. Proceed as directed in (a) except that this smaller 

 quantity of the sample is taken for the determination. 



SUCROSE. 



15 By Reducing Sugars Before and After Inversion. — Tentative. 



Proceed as directed under VIII, 18, using the method given under VlJI, 25, for 



the determination of reducing sugars. 



16 By Polarization. — Tentative. 



Polarize part of the filtrate, obtained in 14, before and after inversion in 

 a 200 mm. tube as directed under VTII, 14 or 16. In calculating the percentage 

 of sucrose the relation of the amount of sample contained in 100 cc. to the normal 

 weight must be taken into consideration. 



17 COMMERCIAL GLUCOSE.-TENTATIVE. 



Polarize a portion of the filtrate, obtained in 14, after inversion in a 200 

 mm. jacketed tube at 87°C. as directed "under IX, 25. In calculating the per- 



