414 Prof. B. Silliman, Jr., on Gibbsite and Allophane. 



I ha\re not had the opportunity of seeing the original memoir of 

 M. Hermann, in which he no doubt details his method of sepa- 

 rating phosphoric acid from alumina. In the Annuaire de Chimie 

 of MM. Millon and Reiset, for 1848, p. 155, an abstract is given 

 of this paper of M. Hermann, which states that the results of 

 Rose's analysis of hydrargillite, in which this chemist detected a 

 small portion of phosphoric acid, led him to the re-analysis of 

 Gibbsite, and that the results of this chemical examination gave 

 the formula already quoted from Rammelsberg in the commence- 

 ment of this article. His analysis of hydrargillite, states 



Water, 



34-54 



Phosphoric acid, . . . . 1*43 



Alumina, 64-03 



10000 



For the separation of phosphoric acid from alumina in Gibbsite, 

 M. Hermann states, as quoted in the Annuaire, that he u dissolved 

 the Gibbsite in hydrochloric acid, and neutralized the solution by 

 chalk — the precipitate obtained on the addition of ammonia was 

 treated by hydrate of soda to dissolve out the alumina. The 

 residue consisted of phosphate of lime." 



2d Analysis. — As before stated, I find the Gibbsite not entirely 

 soluble in hydrochloric acid. I therefore dissolved it in caustic 

 soda, acidulated the solution with hydrochloric acid, neutralized 

 with limewater, precipitated by ammonia, collected the precipi- 

 tate by filtration, and re-dissolved the alumina by caustic soda. A 

 small residue insoluble in this menstruum remained ( = *036 grm.) 

 which was presumed to be phosphate of lime colored by a little 

 phosphate of iron. It is to be remarked, however, that the blow- 

 pipe gave very equivocal evidence of this precipitate containing 

 any phosphoric acid. The alumina was then separated by carb. 

 ammonia and weighed. The results of this analysis were on 

 1-0447 grammes substance taken : 



Al -67859 grm. =64 955 



» * » 



P -00751 « .590 



S I -35000* « M t n n 



Mg S -300 



In sol. -00800 -082 



104470 ] 00000 



3d Analysis. — This last result was confirmed by the analysis 

 of another portion of the mineral by the method proposed by 

 Rammelsberg for the separation of phosphoric acid and alumina. 



* By the difference. 



