40 Sir Robert Kane on the. Composition and Characters 



By boiling, the whole of the iron separated as perphosphate, 

 and was collected, ignited, and the quantity of oxide of iron 

 calculated from its weight. 



For the determination of the chlorine, a totally distinct 

 portion of ash was taken, digested with water, acidulated with 

 nitric acid, and then precipitated with nitrate of silver in the 

 usual way. 



It will be observed that, in all its main features, this plan 

 of examination of the ash coincides with that employed by 

 Will and Fresenius, and proposed by them in iheir memoir 

 on the Composition of certain Ashes. It is, however, that 

 which I had followed in all my former ash analyses, except 

 in regard to the determination of the phosphoric acid, for 

 which I had previously made use of the method proposed by 

 Schulze, but now replaced with so much advantage by that 

 invented by Will. 



It is necessar}', however, to remark, that the composition 

 of the perphosphate of iron, given by Will, and upon which 

 he founds his mode of determining the quantity of oxide of 

 iron, has been contested very recently by Wittstein, who has 

 not succeeded in preparing that salt with the composition 

 assigned to it by Will. According to the latter chemist, it 

 consists, in its anhydrous form, of 2Fe2 Og + SPOg, that is, 



SFegOg ... 160 4289 



3PO5 .... 213 57-11 



373 100-00 



whilst the salt uniformly obtained by the other chemists was 



Fe^Og+PO.y or 



Fcg O3 . . . . 80 52-98 



PO5 .... 71 47-02 



151 100-00 



But the circumstances of preparation of the different salts do 

 not appear to have been quite identical ; and I do not, there- 

 fore, reject Will's numbers, which have been, moreover, 

 verified by some trials made in my own laboratory. I have 

 consequently employed his formula in calculating the amount 

 of iron in the different materials; but it is easy to calculate, 

 for each analysis, the change (in most cases trifling) which the 

 employment of Wittstein's formula for the perphosphate should 

 introduce. 



In the examination of the soils, the process consisted, first, 

 in mechanically separating the sandy and gravelly materials 

 from the finely-divided portion, by careful elutrialion with the 

 smallest possible quantity of pure water. This having been 



