88 PROVISIONAL METHODS FOR ANALYSIS OF FOODS. 



Arsenic may be detected or determined by the Marsh apparatus if combustion 

 be effected by the method given under the determination of phosphoric acid 

 (p. 86). 



Copper may be precipitated electrolytically a in 500 cc of the undiluted wine by 

 using as electrodes pieces of platinum foil 3 by 15 cm. 



19. DETERMINATION OF BARIUM AND STRONTIUM. b 



Evaporate to dryness 100 cc of wine, incinerate as directed under the determina- 

 tion of ash (p. 83), dissolve in dilute hydrochloric acid, evaporate to dryness, and 

 examine the residue spectroscopically. If barium or strontium be present, fuse 

 with sodium carbonate to decompose silicates, dissolve in water and determine by 

 precipitation with sulphuric acid. 



20. DETECTION OF FOREIGN COLORING MATTER. 



Follow directions given under Coloring Matter (pp. Ill and following). 

 21. DETECTION OF NITRATES. 

 (a) WHITE WINE. 



Treat a few drops of the wine in a porcelain dish with 2 or 3 cc of concentrated 

 sulphuric acid which contains about 0.1 gram of diphenylamin d per 100 cc. The 

 deep blue color formed in the presence of nitrates appears so quickly that it is not 

 obscured, even in sweet wine, by the blackening produced by the action of sulphuric 

 acid on the sugur. 



(b) RED WINE. 



Clarify with basic lead acetate and remove the excess of lead with sodium 

 sulphate, as directed under the determination of sugar (p. 84). Filter, and treat a 

 few drops of the filtrate as directed under (a). 



22. DETECTION OF PRESERVATIVES. 



The preservatives to be tested for in wines are salicylic acid, benzoic acid, saccharin, 

 abrastol, hydronaphthol, boric acid, borofluorids, and silicofluorids. Of these the 

 salicylic and benzoic acids are both somewhat commonly employed. Abrastol is 

 said to be used to some extent in Europe, but has not yet been reported in American 

 wines. Hydronaphthol has been used in rare instances, and is still used with suffi- 

 cient frequency to warrant more consideration than it usually receives from food 

 laboratories. Boric acid is better known as a preservative for milk and meat prepara- 

 tions than for fruit and fruit preparations. It is sometimes used, however, in both 

 wine and beer. Its detection is a somewhat more complicated matter than is the 

 case with the other preservatives, because a small amount of boric acid is normal to 

 wines. It is sometimes a difficult matter to fix the amount which may naturally 

 occur. In order to make this test of practical value, therefore, it is essential that 

 the determination of boric acid should be quantitative. The alkaline fluorids, as well 

 as the alkaline borofluorids and silicofluorids, are coming into somewhat general use 

 now as food preservatives, although they have not been frequently reported in wines. 



Fruhauf and Ursic, Bericht u. die Versammlung Oesterreichischer Oenomiker in Bozen, 1886, p. 66; 

 Borgmann, Anal, des Weines, 2d ed., p. 146. 



b Borgmann, Anal, des Weinea, 2d ed., p. 143. 



R. Fresenius, Ztschr. anal. Chem., 1890, 29, 20, 143 and 413; 1891, 30, 18, 452 and 583; 1893, 32, 189 

 and 312. 



JEgger, Arch. Hyg., 2, 373. 



