230 



Gooch and Austin — Determination of 



once formed. The ammonium chloride for this work was 

 prepared pure by boiling the chemically pure salt of commerce 

 with a faint excess of ammonium hydrate and filtering — to 

 free it from traces of iron, silica and alumina. In the first 

 series of experiments dilute ammonia was added slowly to the 

 hot faintly acidulated solution containing the manganoua chlo- 

 ride and more than enough, theoretically, of a saturated 

 solution of microcosmic salt to precipitate the manganese 

 present. The liquid was heated and stirred until the fiocky 

 mass was changed to a crystalline condition. The addition of 

 ammonia drop by drop, with constant stirring and heating, was 

 continued until the manganese was all precipitated in crystalline 

 form. A slight excess of ammonia was added and the liquid 

 with the precipitate was allowed to stand for a half hour, cool- 

 ing gradually or chilled in ice water. The precipitate was 

 filtered off on asbestos under pressure, washed carefully in 

 water made faintly ammoniacal, dried and ignited. The filtrates 

 were tested for manganese by treatment with bromine and 

 heating. The results of these experiments are given in the 



following table. 



















Table I. 









M112P2O7 equiva- 

 lent to MnCl 2 . 



Taken. Found. 



Error in 

 terms of 

 Mn a P 2 7 . 



Error in 



terms of 



Manganese. 



Saturated 



solution of 



TINH 4 NaP0 4 . 



4H 2 0. 



Total 

 vol. 



Manga- 

 nese 

 in 



grm. 



grm. 



grm. 



grm. 



cm 8 . 



cra :i . 



filtrate 



0-4033 



0-3769 



0-0264 — 



0-0102 — 



5 



60* 



none 



0*4033 



0-3728 



0-0305 — 



001.18 — 



5 



60* 



u 



0*3770 



0-3530 



0-0240 — 



0-0090 — 



5 



60 



u 



0-.3770 



0-3620 



0-0150 — 



0-0058 — 



5 



60 



u 



0-4033 



0-3751 



0-0282 — 



0-0109 — 



10 



60 



tt 



0-4033 



0-3774 



0-0259 — 



o-oioo — 



10 



60 



u 



0-4033 



0-3871 



0-0162 — 



0-0062 — 



5 



200 



it 



0-3226 



0-3006 



0-0160 — 



0-0062 — 



5 



200 



a 



* Chilled in ice-water. 



In this method of precipitation of the manganese in a pure 

 solution of a manganous salt the results are all wrong. The pro- 

 portion of the trimanganous phosphate to the pyrophosphate 

 in the residue, calculated from the symbols and the weights 

 taken and found, is in the average two to five. That is to say, 

 five-sevenths of the trimanganous phosphate has been converted 

 to the form of the ammonium manganous phosphate. 



The precipitate obtained in this manner is white and granular 

 but not silky, and after ignition it shows the same dead white 

 color, and is powdery. Evidently the regulation of the volume 

 in which the precipitation is made is not essential, and the 

 chilling of the liquid, is of no importance in changing the 



