26 



ANALYTICAL WORK. 



Place the weighed i^ortiou of dried apples in a roomy platinum disli 

 and lieat cautiously over a low buuseu flame till the mass is thoroughly 

 dry and ignition sets in. The flame is then removed and combustion 

 allowed to proceed spontaneously. Should the burning cease it is to 

 be reinstituted with the aid of the lamj). As a rule, however, the ap- 

 ples will burn of themselves. When the mass is all converted into 

 ash and char, it is to be ground up in a porcelain mortar and ex- 

 tracted with hydrochloric or nitric acid. In the samples done in this 

 laboratory hydrochloric acid was used. The residual charcoal is burnt 

 to a white ash in the same platinum dish, the ash taken up in hydro- 

 chloric acid and the solution added to that first obtained. This solu- ^ 

 tion is then filtered. To the filtrate bromine water is added to oxidize 

 the iron, and the excess of bromine removed. A drop of methyl orange 

 solution is placed in the solution and ammonia added till the reaction J 

 is only faintly though distinctly acid. Without regarding the precipi- f 

 tate produced, add 50 cc of a solution of ammonium acetate containing 

 250 grams of the commercial salt (Hess's method). The temperature is 

 then carried to 70° or 80° and the liquid filtered into a liter flask. It is 

 then washed with water of the same temperature till free of chlorids, 

 though so much washing is hardly necessary in view of the limited 

 amount of zinc oxid likely to be present. The filtrate is treated with 

 hydrogen sulphid till saturated, allowed to stand till the zinc sulphid 

 settles, and then filtered through an ashless filter. The filter is washed 

 with a saturated solution of hydrogen sulphid containing a little acetic 

 acid. Frequently, owing to the well-known peculiarities of zinc sul- 

 phid, it becomes necessary to return the filtrate several times. 



The washed precipitate and containing filter are burnt in a porcelain 

 or platinum crucible, highly ignited and weighed as zinc oxid. Eesults 

 are good, though sometimes a little high, owing to coprecipitated iron ! 

 phosphate. In a portion of 200 grams of fresh apples, to which was 

 added a solution of zinc nitrate corresponding to 9.7 milligrams of 

 oxid, 9.8 milligrams were recovered in one case, 10.3 in another. In 

 another portion, to which 19.4 milligrams were added, 18.9 milligrams 

 were recovered. Check samples of the same apples gave no zinc. 



In the case of the samples analyzed, from 150 to 450 grams, depend- 

 ing on the size of the sample, were taken for each sample, burnt, and 

 treated as described above, and dissolved. The resulting solution was 

 made up to 300 cc, and duplicate portions of 50 cc each taken for analysis. 

 In nearly all cases 450 grams were employed, and the 50 cc portions ^ 

 therefore represented 75 grams. j 



DESCRIPTION OF EVAPORATED APPLES AND OTHER ARTICLES ANALYZED. 



No. 14075. From Seggermann Bros., 165 Duane street, New York; sample of parcel 

 packed by dealer iu Wayne County, N. Y., who buys from small manufacturers and ' 

 makes one bulk of different lots received from different people. 



