.vylntdldgenc^ afidMiscelkm€omj4r(icies. ^ * Si S 



Eifter ■««liicli, what remainecfe, as also of lithia, were estimated in the 

 manner previously describied/- In another fcxj)criment, the mass, after 

 having been heated to redness, was fused with silica and silicate of 

 soda, the lithia being leftifcHitf 4f oonsid^ration. Therefeults were as 

 follows:— ('dot- ri.- 



Phosphoric acid .. 2^^''^ 22^73 •"'>''i^2-e4^^^^t'1 = 24-36 

 Alumina 3&m ' S8-'ll fiflimul^ = 35-08 



., i,hit\mH^^i^tiUi'h*'1nii7,iii^ in\n3:jh n a'mlnoo oJ :ti bSijss • 9^84 

 Water.. ..fl«fcHS^.>j>^?:jOa. .iHa^flftimi aim* o//} li0f»t.aO'72 



'><^i(kh'Maa'W<tile^foll6Alaiig'ferifi'uM,^*^'^'-' onni^omU idiml^. i. 



-ornil «uiJ ^.fiirnnij-x'j !o |j(i^i.(V<o(((j<^ .jI} i(iT*.li ■^unomi lo TfJinuliorf 

 to .pkS .v/rnul/I miiilliW Jii nriiinom -jdl V) brjidabni ms I ,oaolH 



But little is at present known concerning', (the composition ' of 

 the artificial compounds of phosphoric acid and alumina. ' Two 

 principal salts are distinguished — 1, neutral, formed by the preci- 



Oiipitation, of a neutral aluminous salt by 2NaO, P2O3, to which, 

 consequently, the composition 2AL O.^, SPc^Oj is assigned; and 2, 

 a basic Sfdt, which is formed by dissolving the former in an acid 

 and precipitating it by excess of ammonia. This is usually re- 



i,;gJMfded as 4AI.2OJ, 3Po Oj, although we are unacquainted with any 

 .^yjalysisof it. We know that a compound of phosphoric acid and 

 alumina is not decomposed by fusion with carbonate of potash, 

 because a large portion of it is dissolved out with the excess 

 of alkali when it is washed with water. Berzelius, in analysing 

 wavellite, made use of a method in which the decomposition was 

 effected by heating it to redness with a mixture of an alkaline car- 

 bonate and silica. Fuchs also used basic silicate of potash with the 

 same view. But Berzelius's method is somewhat tedious, and the 

 addition of silica always causes a portion of it to remain in the alka- 

 line liquid, and on evaporating it and adding carbonate of ammonia 

 it cannot be entirely removed. This is more completely effected by 

 using a solution of oxide of zinc in carbonate of ammonia, but the 

 subsequent separation of the zinc renders the process still more com- 

 plex. The object is attained more rapidly by dissolving the sub- 

 stanch in a sufficient quantity of sulphuric acid which has been pre- 

 viously diluted with an equtd bulk of water, and then adding a 

 proper quantity of potash, which is also dissolved by heat. The 

 whole is then mixed with a considerable quantity of alcohol of 0'863 

 sp. gr., and set aside for some hours. Alum and sulphate of potash 

 then separate, whilst the sulphuric and phosphoric acids remain in 

 solution. It is filtered, washed with alcohol, the residue dissolved 

 in water and the alumina precipitated by ammonia. The alkaline 

 filtrate is treated with water, evaporated until the alcohol is removed, 

 supersaturated with ammonia (whereby a few millegrammes of a pre- 

 cipitate are produced, arising from a trace of alumina) and precipitated 

 with chloride of calcium. The precipitated liquid should be filtered 

 with exclusion of the air, as it constantly contains sulphate of lime ; 



