Diagnostic methods, chemical, bacteriological and microscopical : a text-book for students and practitioners . ings or Purdys solution, using all theprecautions mentioned under these tests in thesection on Urine. Ten of FehHngs solu-tion are reduced by gram of lactose,while the 35 of Purdys solution are re-duced by gram of lactose. If the polarimeter is to be used for theestimation of lactose in milk the followingprocedure may be used. Fifty of the well-mixed milk are placed in a flask, 25 of asolution of neutral lead acetate are added, the flask is closed wi
Diagnostic methods, chemical, bacteriological and microscopical : a text-book for students and practitioners . ings or Purdys solution, using all theprecautions mentioned under these tests in thesection on Urine. Ten of FehHngs solu-tion are reduced by gram of lactose,while the 35 of Purdys solution are re-duced by gram of lactose. If the polarimeter is to be used for theestimation of lactose in milk the followingprocedure may be used. Fifty of the well-mixed milk are placed in a flask, 25 of asolution of neutral lead acetate are added, the flask is closed with a stopperthrough which passes a glass tube approximately 30 cm. in length. Themixture is then heated over a small flame to boiling. After the mixture hascooled it is filtered through a dry filter into a dry vessel and polarized. (10). Preservatives in Cows Milk,(a). Sodium hide the acid reaction of a spoiled sample of milk sodium carbonateis often added, and may be detected as follows: Ten of milk are mixedwith ten of 96 per cent, alcohol and a drop of rosolic acid solution. Pure. Fig. 164.—Soxhlet apparatus.{Hawk.) SECRETION OF THE MAMMARY GLANDS. 609 unadulterated milk produced a brownish-yellow color, but, in the presenceof sodium carbonate or bicarbonate, a rose color is obtained. For greaterprecision in doubtful cases the questionable sample should be compared withknown unadultered milk. Phenol-phthalein solution may be used as an in-dicator in place of rosolic acid. By this method per cent, of carbonatesmay easily be detected. {b). Salicylic Acid. Twenty of milk are treated with two or three drops of sulphuric acidand shaken with an equal amount of ether. The greatest possible part of theethereal solution is drawn off and evaporated, the residue extracted with40 per cent, alcohol, filtered, and 5 of the filtrate treated with a few dropsof ferric chlorid solution. A violet color shows the presence of salicylicacid or some other hy
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