328 Knopf and Schaller — Two Xew Boron Minerals. 



results, due to the retention of boric acid. It seems as if the 

 presence of so much iron had a very great tendency to retain 

 some of the boric acid, for the lowest gravimetric determina- 

 tions of iron were several per cent higher than the volumetric 

 ones, even though the solutions of iron chloride were repeat- 

 edly evaporated with methyl alcohol. The ferrous iron was 

 determined by a modification of Pratt's method, which lias 

 been shown (Hillebrand) to give reliable values.* The water 

 was determined by heating the mineral (size <^20> 60 mesh) 

 in a glass tube and weighing the water directly in a portion of 

 that tube (Penfield's method). The boric acid was deter- 

 mined by fusing the mineral with sodium carbonate, leaching 

 with water, refusing the residue, acidifying the solution with 

 nitric acid, distilling with methyl alcohol, collecting in ammo- 

 nia, and finally weighing boric acid as calcium borate. 



The ratios obtained from the average analysis are shown 

 below, the proportion of magnetite present being obtained as 

 presently to be described. 



*Bull. 305, U. S. Geol. Survey, p. 138. Both of the two new borates 

 here described dissolve readily in hydrofluoric acid, so that no difficulty was 

 had in rapidly making the ferrous iron determinations. The powder was 

 always coarser than 100 mesh and for the paigeite coarser than 60 mesh, so 

 that very little, if any, oxidation of the ferrous iron resulted from the 

 grinding. That such oxidation occurs, sometimes to a large extent, has 

 recently been shown by Mauzelius (Sveriges Geol. Undersokning, Yearbook 

 I, 1907', No. 3. See Client. Abstracts, 1907. 2861, for an abstract of the 

 article). For the paigeite samples the oxidation caused by grinding is con- 

 siderable, the value for ferrous iron falling from 44 48 per cent (on<^20> 60 

 mesh) to 39 per cent on the finely ground material. The direct determina- 

 tion of total water was similarly made on coarse material, so that the amount 

 of hydroscopic water in the sample was a minimum. What increase in the 

 water (given off at 110°) is caused by grinding these borates is not known, 

 but the following results made on ludwigite from Hungary (a mineral of 

 analogous composition) show that a very considerable amount of water is 

 taken on by the mineral during grinding. Direct duplicate determinations 

 of water at 110° on powder of <10> 20 mesh gave : 



(1) 0-09 per cent. (2) 0-12 per cent. 



On same powder finely ground : 



(1) 050 per cent. (2) - 52 per cent. 



Therefore a total water determination on a mineral such as these borates 

 must, to be of any value, be made on coarse material such as was used for 

 hulsite and paigeite. It is therefore believed that the water content given 

 for these minerals is an essential part of their composition and is not to be 

 taken as hydroscopic or accessory water. However, the question is still an 

 undecided one as to just what role the water plays and it may be that future 

 work will show that the water content of these two minerals is extraneous 

 and does not actually belong to the minerals themselves. See a paper soon 

 to be published by Dr. Hillebrand for a discussion of the effect of grinding 

 on the water content, as well as on the oxidation of ferrous iron. To Dr. 

 Hillebrand the writer is under obligation for calling his attention to these 

 points, which served to explain the very vaiying results first obtained on 

 paigeite for ferrous iron. Data showing the oxidation of ferrous iron for 

 these borates as well as for other minerals will be given in a later paper. 



