WTNE. 



87 



si UK .iint of tnrtaric acid necessary to combine with all the ash (considering It 

 t> msist entirely of potash). Deduct the figure so obtained from the total 

 t:irlaric acid for the free tartaric arid. 



16. Crude Protein. Provisional. 



Determine nitrogen in HO <r of wine by the Kjeldahl or Gunning method (see 

 page .".. under " I. Fertilizers") and multiply the result so obtained by 6.25. 



17. Sugar. 

 (a) BY REDUCTION. PROVISIONAL. 



Place 200 cc of wine in a porcelain dish, exactly neutralize with an approxi- 

 mately normal sodium hydroxid, using litmus paper as indicator, and evaporate 

 to about one-fourth the original volume. Transfer to a 200 cc flask, add suffi- 

 cient normal lead acetate to clarify, dilute to the mark with water, shake, and 

 filter through a folded filter. Remove the lead and determine reducing sugars 

 before and after inversion by the Soxhlet method, page 42, under " VI. General 

 Methods." 



(b) BY POLARIZATION. PROVISIONAL. 



Polarize part of the filtrate obtained in (a), before and after inversion, in a 

 200 mm tube as directed under " VI. General Methods," page 40, to obtain the 

 polarization of the wine in the original dilution. In calculating the percentage 

 of sucrose the relation of the amount of sample to the normal weight must be 

 taken into consideration. 



18. Commercial Glucose. Provisional. 



Wine polarizing over 0.9 to the right and containing not more than 0.1 per 

 _cent of reducing sugar may have been prepared from glucose, and should be 

 treated as follows : 



Dealcoholize 200 cc of wine by evaporating to about one-fourth its volume, 

 and add enough water to the residue to make its sugar content less than 15 per 

 cent. For the purpose of this operation the sugar content of the wine may be 

 assumed to be 2 per cent less than the extract. Add 2 or 3 grams of compressed 

 yeast, let stand at about 25 C. for four or five days, when fermentation will be 

 complete. Evaporate the fermented liquid in a porcelain dish to a thin sirup, 

 after the addition of a little sand and a few drops of a 20 per cent solution of 

 -him acetate and acetic acid. To the residue add 200 cc of 00 per cent 

 alcohol, with contant stirring. Separate the alcohol solution by filtration and 

 evaporate until about 5 cc remain. Mix the residue with washed boneblack, 

 filter into a graduated cylinder, and wash until the filtrate (cooled to 15 

 amounts to 30 cc. When the filtrate shows a dextrorotation of more than LO . 

 it indicates the presence of the unfermentable constituents of commercial glu- 

 cose. Results by this method are not reliable with wines that are heavily 

 preserved. ' 



19. Gum and Dextrin. Provisional. 



Evaporate 100 cc of wine to about 10 cc and add 10 cc of 96 per cent alcohol. 

 If gum or dextrin be present (indicated by the formation of a voluminous pre- 

 cipitate), continue the addition of alcohol slowly and with stirring until 100 cc 

 have been added. Let stand over night, filter, and wash with 80 per cent alcohol 

 by volume. The precipitate may then be dried and weighed, or it may be treated 



