The Phosphates of America. 153- 



evaporated to a small bulk. When organic matter is present, it is 

 desirable to evaporate to pastiness, that the acid may partially de- 

 compose it. The solution is now washed into a beaker with about 

 50 to 100 c.c. water ; boiled for a short time with bromine or other 

 oxidizing agent, as suggested by H. H. B. Shepherd (in Chem* 

 News, 63, 251) ; and, after adding ammonia, it is again boiled for 

 about half an hour. It is then cooled, and, after the addition of 

 a little more ammonia, is filtered ; washed with a hot solution of 

 ammonium chloride to prevent the precipitate from passing through 

 the filter ; ignited, and weighed. The phosphoric acid is determined 

 by dissolving the ignited precipitate, exactly as we have described 

 in the former method, and the oxides of iron and alumina are 

 obtained by difference. If magnesia is present, the phosphates of 

 iron and alumina obtained as above must be freed from this im- 

 purity by washing the precipitate off the filter, and boiling with 

 water and a little nitrate of ammonium. 



As we have already stated, our own preferences are in favor of 

 the first method, and this, not only because we believe it to be per- 

 fectly exact and reliable, when in the hands of a skilful operator,, 

 but because it is much more rapid and much less costly. We r 

 however, have no positive objections to the Glaser scheme, and 

 when carried out on the above lines should have every confidence 

 in the accuracy of its results. 



Lime (CaO). 



The total filtrates from the iron and alumina determination first 

 described are mixed by shaking the flask, and are then concen- 

 trated by boiling down to about 100 c.c. At this point there are 

 added to the liquid about 20 c.c. of a saturated solution of am- 

 monium oxalate, and the mixture, after stirring, is withdrawn 

 from the fire, covered with a watch-glass and allowed to stand 

 for six hours. At the end of this time the supernatant fluid is 

 filtered through an ashless filter ; the residue is washed three times 

 by decantation with boiling water, and then brought upon the 

 filter, and the beaker and filter are thoroughly washed at least 

 three times more. The filter is then dried, taken from the funnel 

 with the greatest care, placed in a tared platinum crucible, and 

 ignited at a low red heat for ten minutes. At the end of this 

 time it is brought to the highest possible temperature by the 

 blast, kept there for five minutes, covered, and then rapidly re- 

 moved to the desiccator. When quite cold it is weighed in the 



