VINEGAR. 67 



expressed in terms indicated in the previously described methods is, for 

 cider vinegar 26 to 65, average 39; for malt vinegar 5.5, and for spirit vinegar 1.1. 

 '/'/// (jii(ii//it>i of frfiosp'lioric <id<l in the ash, expressed in milligrams per 100 grams of 

 the vinegar, ranges in case of pure cider vinegar from 9 to 39; in malt vinegar it is 

 variously stated to range from 9 to 12.5 and from 50 to 100; while the ash of spirit 

 vinegar shows traces only. The solubility of the phosphoric acid in cider vinegar is 

 high, 50 to 75 per cent of the amount present being soluble in water, or from 4.7 to 

 22.7 mg per 100 grams of vinegar; no soluble phosphoric acid is found in the ash of 

 spirit vinegar. If cider vinegars be diluted with hard water, the relatively insoluble 

 earthy phosphates are formed and the proportion of soluble phosphoric acid greatly 

 reduced. 



The flame reaction obtained by igniting a drop of the solids upon a loop of platinum 

 wire in a colorless flame is, in case of cider vinegar, exclusively that of potash; solids 

 obtained from artificially colored vinegars, sugar, spirit, and glucose vinegars always 

 give the sodium flame. b 



The optical activity of vinegars is often characteristic. For this purpose they should 

 be examined in a 400-mm tube, after treatment with lead subacetate or boneblack, 

 if necessary, for their clarification. Pure cider vinegar is slightly laevorotatory, rang- 

 ing from 0.96 to 2.79 Ventzke, in thoroughly acetified samples. Vinegar con- 

 taining unfermented apple solids will be much more highly Ijevorotatory; wine vin- 

 egar -is also slightly Itevorotatory. On the other hand, vinegar from sugarhouse 

 wastes ia dextrorotatory before and hevorotatory after inversion; that from glucose 

 dextrorotatory both before and after inversion. Incompletely acetified vinegar 

 made from incompletely fermented cider might exhibit the optical properties of a 

 mixture of spirit vinegar and cider jelly, but the latter would be distinguished by 

 differences at other points. 



The ratio of reducing miytirx, nflcr imrmnn, to total solids is a means of distinguish- 

 ing genuine cider vinegar from spirit vinegar supplied with solids from cider jelly. 

 Where they constitute 50 per cent or more of the solids, the vinegar may be regarded 

 as not pure cider vinegar. An incompletely fermented cider which had begun acet- 

 ilication might be mistaken for the imitation product if this ratio alone were con- 

 sidered; but low acetic acid, high alcohol, and other characters, make it easy to dis- 

 tinguish the former. The determination should be made as follows: Pipette 25 cc 

 of the vinegar into a 100-cc flask; add 5 cc of concentrated hydrochloric acid; heat 

 the flask in a water bath at 70 C., and after the vinegar has attained a temperature 

 of 67, maintain it at 67 to 70 for five minutes; then cool. Dilute one half; neu- 

 tralize exactly with sodium hydroxid solution, using phenolphthalein as an indi- 

 cator; make up to 100 cc and withdraw 25 cc for determination of reducing sugar 

 by the copper-reduction method of Allihn, computing the results by the table of 

 Meissl and Wein. d In case a large ratio of reducing sugar to total solids be found, 

 its origin whether from cider jelly, sugarhouse wastes, or glucose remains to be 

 determined, either by collateral evidence or by a more detailed separation of the 

 several sugars in the solids. For the latter purpose, employ the methods described 

 by Browne. e 



The ratio of ash to solids is also indicative. In cider vinegar the ratio ranges from 



Smith, A. W., Jour. Am. Chcm. Soc., 1898, 20, 7; Blyth, Foods: Their Comp. and Anal., 4th ed., 

 p. :>s7; Hehner, Vtjschr. Chem., Nahr, 1893,7, 194. 



' Davenport, 26th Ann. Kept. Milk Inspector, City of Boston, 1885. 



"Frear, Kept. Pa. of Dept. of Agr., 1898, p. 145; C. A. Browne, jr., Kept. Pa. State College Agr. Exp. 

 Station, 1900, p. 2<;n; also Bulletin 58, Pa. Dept. of Agr., p. 43; Doolittle & Hess, Jour. Am. Chem. 

 Soc., 1900, 22, 19; Allen, Com'l Organic Analysis, second edition, Vol. I, p. 81; Von Bitteryst, Rev. 

 nils, internal., 1894, 7, 151. 



i Wiley, Agricultural Analysis, Vol. Ill, p. LW. 



Kept. Pa. State College Agr. Kxpt. sta.. I'.xx), p. 269-274; Cf. also, Frear, Kept. Pa. Dept. of Agr., 

 1898, p. 138 and following, and Browne, Bui. 58, Pa. Dept. of Agr., for comparative data. 



