FERMENTED AND DISTILLED LIQUORS. 87 



ceases. Add about 75 cc concentrated nitric acid, warm gently, and finally evaporate 

 almost to dryness. Then add 10 cc of concentrated sulphuric acid and a little mer- 

 cury and boil till the solution clears. a Employ the official volumetric method for 

 phosphoric acid, as stated above. 



16. DETERMINATION OF TARTARIC ACID AND TARTRATES. 



(a) TOTAL TARTARIC ACID. b 



To 100 cc of wine add 2 cc of glacial acetic acid, 3 drops of a 20 per cent solution of 

 potassium acetate, and 15 grams of powdered potassium chlorid, and stir to hasten 

 solution. Add 15 cc of 95 percent alcohol (sp. gr. 0.81) and rub the side of the 

 beaker vigorously with a glass rod for about 1 minute to start crystallization. 

 Let stand at least 15 hours at room temperature; decant the liquid from the separated 

 acid potassium tartrate as rapidly as possible (using vacuum) through a Gooch cru- 

 cible prepared with a very thin film of asbestos, transferring no more of the precipi- 

 tate to the crucible than necessary. Wash the precipitate and filter three times with 

 a small amount of a mixture of 15 grams potassium chlorid, 20 cc of 95 per cent alco- 

 hol (sp. gr. 0.81), and 100 cc water, using not more than 20 cc of the 'wash solution 

 in all. Transfer the asbestos film and precipitate to the beaker in which the precipi- 

 tation took place, wah out the Gooch crucible with hot water, add about 50 cc of 

 hot water, heat to boiling, and titrate the hot solution with decinormal sodium 

 hydroxid, using delicate litmus tincture or litmus paper as indicator. Increase 

 the number of cubic centimeters of decinormal alkali employed by 1.5 on account 

 of the solubility of the precipitate. This figure multiplied by 0.015 gives the amount 

 of total tartaric acid in grams per 100 cc. 



(b) CREAM OF TARTAR. 



Ignite the residue obtained from the evaporation of 50 cc of wine as directed under 

 the determination of ash. Exhaust the ash with hot water, add to the filtrate 25 cc 

 of decinormal hydrochloric acid, heat to incipient boiling and titrate with decinor- 

 mal alkali solution, using litmus as indicator. Deduct from 25 cc the number of 

 cubic centimeters of decinormal alkali employed and multiply the remainder by 

 0.0188 for potassium bitartrate expressed in grams. 



(C) FREE TARTARIC ACID. 



Add 25 cc of decinormal hydrochloric acid to the ash of 50 cc of wine, heat to 

 incipient boiling and titrate with decinormal sodium hydroxid, using litmus as indi- 

 cator. Deduct the number of cubic centimeters of alkali employed from 25 and 

 multiply the remainder by 0.0075 to obtain the amount of tartaric acid necessary to 

 combine with all the ash (considering it to consist entirely of potash). Deduct 

 the figure so obtained from the total tartaric acid for the free tartaric acid. 



17. DETERMINATION OF PROTEIN. 



Determine nitrogen in 50 cc of wine by the Kjeldahl or the Gunning method, and 

 multiply the result so obtained by 6.25. 



18. DETERMINATION OF HEAVY METALS. 



Lead is often found in wine as a result of the use of shot in cleaning bottles, and 

 copper and arsenic may occur in wine made from grapes sprayed with insecticides. 

 Lea<l and copper may be determined in 500 or 1,000 cc by the method given under 



Vegetables. 



Glaccrand Miihlc, Clu'in. /(#.. ls%, '20, 7i:>. 



' Halt-tike mid Mosliiitfcr, Ztschr. anal, Clu-in.. l.v.tfi, 84, 263. 



