32 



From 50 to 100 c.c. of milk are precipitated with a few drops 

 of muriatic acid. After lieating to boiling, the solution is filtered 

 from the precipitate, and the latter washed. The solution is then 

 evaporated to about 35 c.c, and again filtered to remove some 

 albumen and fat, which have become insoluble during the concen- 

 tration of the liquid. The concentration of the fluid is then con- 

 tinued until about 10 c.c. remain. These are distributed into 

 three test tubes, one being used for the determination of the 

 presence of zinc, another for copper, and the last for lead. 



The presence of sine is determined by means of sulphuretted 

 hydrogen passed through the, almost neutralized solution. A 

 white precipitate would indicate the presence of zinc. Frequently 

 sulphur is precipitated, which, however, on heating on platinum 

 foil, burns without leaving a residue. The precipitate is there- 

 fore to be more closely examined. The hydrochloric solution 

 is made alkaline with ammonia, and sulphide of ammonia added, 

 when a white flocculent precipitate will be formed in the presence 

 of zinc. In case that only small quantities of zinc are present, 

 white tunbidity ensues, and the precipitate becomes flocculent only 

 after long standing. 



Lead is found in the hydrochloric solution by passing sulphu- 

 retted hydrogen through it, which produces a grayish-black pre- 

 cipitate. Chromate of potassium produces a yellow precipitate of 

 chromate of lead. 



In the presence of copper, ammonia produces a dirty gray 

 color ; potassium ferrocyanide a brownish-red color, or precipitate. 

 If some of the solution be brought on a clean piece of platinum 

 foil, and a clean knife be laid upon it, the latter becomes, in the 

 course of several hours, coated with a layer of red metallic copper 



If these metals are present in only mimite quantities, it is bet- 

 ter to destroy the albuminous matter by means of hydrochloric 

 acid and chlorate of potassium. The rest of the operation remains 

 the same. 



Vegetable poisons : A case is on record wherein, in the City 

 of Kome, twenty-one persons were poisoned, in the year 1875, by 

 the milk of goats which had fed upon momordica, the fruits of 

 which are known to possess highly purgative properties. The pa- 

 tients recovered under medical treatment. 



