238 METHODS OF ANALYSIS [Chap. 



centage of glucose the relation of the amount of sample contained in 100 cc. to the 

 normal weight for the instrument must be taken into consideration. 



18 ASH— TENTATIVE. 



Proceed as directed under VIII, 4, employing the residue from 50 cc. of the wine. 



"19 ASH-EXTRACT RATIO.— TENTATIVE. 



Express results as 1 : x, in which x is the quotient obtained by dividing the 

 grams of extract per 100 cc. by the grams of ash per 100 cc. 



20 ALKALINITY OF THE WATER-SOLUBLE ASH.— TENTATIVE. 



Extract the ash, obtained as directed under 18, with successive small portions 

 of hot water until the filtrate amounts to about 60 cc. and proceed as directed under 

 IX, 18. Express the alkalinity in terms of the number of cc. of N/10 acid required 

 to neutralize the water-soluble ash from 100 cc. of the wine. 



21 ALKALINITY OF THE WATER-INSOLUBLE ASH.— TENTATIVE. 



Ignite the filter and residue from 20 in the platinum dish in which the wine was 

 ashed, and proceed as directed under DC, 19. Express the alkalinity in terms of 

 the number of cc. of N/10 acid required to neutralize the water-insoluble ash from 

 100 cc. of the wine. 



22 PHOSPHORIC ACID.— TENTATIVE. 



Dissolve the ash, obtained as directed under 18, in 50 cc. of boiling nitric acid 

 (1 to 9), filter, wash the filter and determine phosphoric acid in the combined filtrate 

 and washings, as directed in I, 6 or 9. If the ash ignites without difficulty, no free 

 phosphoric acid need be suspected. Should there be any free acid, the ash remains 

 black even after repeated leaching. In such cases calcimn acetate or a mixture 

 containing 3 parts of sodium carbonate and 1 of sodivun nitrate should be added 

 to avoid loss of phosphoric acid before attempting to ash. 



23 SULPHURIC ACID.— TENTATIVE. 



Precipitate directly the sulphuric acid in 50 cc. of the wine by means of barium 

 chlorid solution, after acidifying with a small excess of hydrochloric acid, and de- 

 termine the resulting barium sulphate as directed under II, 20. Allow the precipi- 

 tate to stand for at least 6 hours before filtering. Report as sulphur trioxid (SOj). 



24 CHLORIN.-TENTATIVE. 



To 100 cc. of dry wine or 50 cc. of sweet wine add sufficient sodium carbonate 

 to make distinctly alkaline. Evaporate to dryness, ignite at a heat not above low 

 redness, cool, extract the residue with hot water, acidify the water extract with 

 nitric acid and determine chlorin as directed under III, 15. 



25 TOTAL ACIDS.— TENTATIVE. 



Measure 20 cc. of the wine into a 250 cc. beaker, heat rapidly to incipient boiling 

 and immediately titrate with N/10 sodium hydroxid. Determine the end point with 

 neutral 0.05% azolitmin solution as an outside indicator. Place the indicator in 

 the cavities of a spot plate and spot the wine into the azolitmin solution. The end 

 point is reached when the color of the indicator remains unchanged by the addition 

 of a few drops of N/10 alkali to the wine. 



