June 2, 1893.J 



SCIENCE. 



301 



Examining into its merits, it is readily seen that this method, 

 as previously stated, is open to several serious objections: phos- 

 phate of aluminium is quite soluble in an excess of acetic acid; 

 the precipitate of the phosphates of iron and aluminium is very 

 apt to carry with it some of the calcium salt; the precipitate of 

 the iron and aluminium obtained is not necessarily pure normal 

 ortho-phosphate; and, finally, there is a great risk of introducing 

 an error in calculating the combined phosphates of iron and 

 aluminium over to the sesqui oxides. 



The molecular masses of the compounds concerned are : — 

 Fe PO4 = 151 

 Al PO4 = 122 

 Fea Og = 160 

 AU Os = 102 

 If the constituents, the iron and the aluminium phosphates, 

 occur in the precipitate in the proportion of their respective mo- 

 lecular masses, i.e., 151:122, no error will be committed in 

 assigning to this precipitate of the mixed phosphates the formulae, 

 (Fe PO4 + Al PO4), and calculating to Fe, O3, as is shown by 

 the following example. Assume the composition of the pre- 

 cipitate to be : — 



Fe PO4 = 0.151 

 AIPO4 =0.122 



FePO, -I- AlPO4 = 0.273 

 Calculating the combined phosphates over to the combined 

 oxides : — 



2 (Fe PO4 -I- Al PO4) : (Fe^ O3 + Al^ O3) :: . 273 : x 

 546 : 262 :: . 273 : x 



X = 0.131 

 i.e., (Fe^Oj + AI2 03)^0.131 

 Calculating the Fe PO4 and the Al PO4 separately over to their 

 respective oxide, and then adding them : — 



2reP04 :Fej O3 :: 0.151 :x 

 3u2 : 160 

 X = 0.080 

 2 AIPO4 :A1, O3 

 244 : 102 

 X = 0.051 



:: 0.151 :x 

 Fe, O3 

 :: 0.122 :x 

 :: 0.122 :x 

 AUG, 



0.0800 Fes O3 

 0.0510 Al, O, 



0.1310 Fe^ O3 -1- AU O3, 



which is identical with the value previously obtained. If, how- 

 ever, the iron phosphate and the aluminium phosphate are present 

 in a proportion different from the one assumed in the above ex- 

 ample, the result obtained by calculating their combined weight 

 to combined oxides is wrong. It will be too high or too low, 

 accordingly as the iron, aluminium, or the phosphate predomi- 

 nates. 



Example. — Assume that the combined phosphates weighed ex- 

 actly the same as before = 0.273 gramme; but assume the com- 

 position of the precipitate to be: — 



Fe PO4 = 0.219 

 Al PO4 = 054 



0.273 

 Calculating the combined phosphates over to the combined ox- 

 ides, of course the same result as previously found will be ob- 

 tained, namely, that 



0.273 = 0.131 



(Fe PO4 -t- Al PO4) (Fej Oj + Alj O3) 

 But calculating the Fe PO4 and the Al PO4 separately to their 

 respective oxide, there is found : — 



If the composition of the same weight of the combined phos- 

 phates of iron and aluminium be assumed to consist of 

 FeP04 0.054 

 AIPO4 0.219 



0.273 



there will result as before :- 



0.273 

 (Fe PO4 + Al PO4) 



(Fe, 



0.131 

 O3 + AU 



O3) 



But, 



FePOj 

 Al PO4 

 FeP04 



+ 

 AlPO, 



0.054 = 0286 Fe^ O3 

 0.219 = 0.0915 Alj O3 



r Fe, O3 



0.273 = 0.1201- + 



( AU O3 



a value considerably lower than obtained by the other method of 

 calculation. 



Method II. makes a much better showing than the preceding 

 method. The chief objection to it, is the error involved in weigh- 

 ing the iron and the aluminium as phosphates and calculating 

 them to the oxides, as explained above. 



This difficulty, however, could be obviated in the following 

 manner: — 



Proceed with the analysis exactly as directed, and weigh the 

 iron and the aluminium as phosphates; then dissolve in Hj SO4 ; 

 reduce the iron by means of zinc and platinum in a Hj SO4 solu- 

 tion; titrate with standardized K, Mn^ Og solution, and record 

 the iron as Fe„ O3 ; calculate this to iron phosphate, Fe PO4 ; sub- 

 tract this value from the weight of the combined phosphates, and 

 then calculate the remainder, the Al PO4 to AU O3. 



Method III. has certainly yielded the most satisfactory result, for 

 the difference between the amount of the iron and the aluminium 

 oxides present and determined is only 0.04 per cent, a difference 

 corresponding to less than two-tenths of a milligramme in the 

 actual weight of the precipitate, Fe, O3 + AU Og, in this experi- 

 ment. 



The feature which serves as the special endorsement of this 

 method is the fact that the constituents sought are reported in 

 the very form in which they are weighed, and that thus the in- 

 troduction of errors by calculation is excluded. 



In order to test the working of these three methods in actual 

 practice they were applied to the analysis of four samples of bone 

 black. 



The results obtained follow : — 



OSTEOL06ICAL NOTES. 



BY DANIEL DENISON SLADE, M.C.Z. , CAMBRIDGE, MASS. 



The jugal arch in the order of the Cetacea presents some singu- 

 lar modifications. In the Delphinoidea, the squamosal, frontal, 

 and jugal enter into its composition. The squamosal sends for- 

 ward a large, bulky process which nearly meets the descending 

 post-orbital process of the frontal. The jugal is an irregular flat 

 bone, covered by the maxilla, and sends back from its anterior 

 and internal border a long and very slender process, curved 

 slightly downwards, to articulate with the short, obtuse process of 

 the squamosal, thereby forming the lower boundary of the orbit. 



So far as the relations of the squamosal and jugal are concerned, 

 the portion of the arch thus formed is a counterpart of that of the 

 horse; although the union of the two bones is much more com- 

 plete in the latter animal. The jugal in the horse is relatively a 

 much larger bone, and sends back a well-developed process which 

 underlies that of the squamosal, with which it is joined by a 



