17"'' On Frtbeuic Phosphoric Acid, 



composition of phosphoric and phosphorous acids, of phos- 

 phates and phosphites, established, as we consider them at 

 the present day. As the history of phosphoric arid subse- 

 quent to L819 is -imply that of analytical methods of separat- 

 ing and determining it. 1 will now present some figures 

 which will answer a> a criticism of the different methods oi 

 separating it from bases. 



The investigation of the methods forseparating tribasic phos- 

 phoric acid tVoin ses<jiiioxi<k's, principally from Besqnioxide of 

 iron, was undertaken with a view of finding a more perfect way 

 of analyzing iron ores, arid has taken me nearly two years for 

 its completion. The analyses were not all commenced in the 

 order in which I give them, yet the object for which they were 

 undertaken was never lost sight of. In spite of much work, 

 and that very tedious, I must confess that I have not succeed- 

 ed in pointing out a course of analysis which will hold good 

 with all iron ores, the varied and manifold constituents of which 

 require verj often a deviation from the rules laid down. 1 hope, 

 however, that the comparative analyses made may serve as an 

 addition to anal} tical chemistry. 



[n the course of this investigation, the necessity was felt of 

 comparing the different way- of determining iron. To this end, 

 pure crystals of twice crystallized green vitriol or sulphate of 

 iron were dissolved in water, and 50 cubic centimetres of this 



solution were used each time for analysis. The particulars 



of the manipulations I may well leave nnmentioned, and only 

 orive the results. In two instances 50c. c. were oxydized with 



pure nitric acid, and while hot, precipitated with ammonia ; 



atb-r washing out with boiling water, until no sulphuric 

 acid could be detected in the filtrate, the precipitates 



were dried and weighed. 1 may mention here, that l<> wash 



out a gramme of hydrated Besquioxide of iron, one gallon at 



I of hot water is required. When the latter is washed out, 



it assumes a more sand j appearance, it runs very easily through 



the filter, and when suspended in water will settle only after 



