330 a E. Munroe on the estimation of Phosphoric Acid. 



I next studied the behavior of aluminic oxide toward phos- 

 phoric acid, and this time met with better success. 



The following course was pureued. To the boihng phospliate 

 solution a weighed quantity of pure aluminic sulphate, pren- 

 ously dissolved, was added. A solution of mercuric chloride 

 was then added, and finally sodic hydrate until a precipitate of 

 mercuric oxide was obtained which remained undissolved. In 

 order to hasten the operation the precipitate was allowed to 

 settle and the supernatant liquid poured upon the filter. The 

 gelatinous precipitate was then evaporated to'complete dryness 

 as before mentioned, filtefred, ignited and weighed. The in- 

 crease of weight, over that of the aluminic oxide used, was 

 phosphoric oxide. It was found extremely difficult to burn the 

 filter. Care must be taken that for every gram of phosphoric 

 oxide at least two grams of aluminic oxide are added. 



The percentage of aluminic oxide, in the sulphate used, was 

 determined bv ignition, ammonic carbonate being used to drive 

 off the last traces of sulphuric oxide. The following result- 

 were obtained : 



(1) -7320 grms. Al2(S04)3 . IfiH.O ffave -JSJO erms. AbOa = 17-89 p. c. 



(2) -7100 « " ^«' •1270 " " =17-87 " 



Mean 17t<8. 



Anhydrous disodic phosphate was the first salt treated. Ij 

 order to work with greater rapidity a solution of known strength 

 was prepared of which 50 cm. a corresponded to '6195 grms. oi 

 phosphate. This gave the following results : 



(1) -619.5 grms. gave -3099 grms. P3O, = 50-02 p. c. 



(2) -619.5 " " -3100 " " =50-03 " 



(3) -6195 " " -3097 » « =50-01 '* 



(4) -6195 " " -3097 " " =50-01 " 



Mean 50-02. Theory 5000. 

 Ammonio-sodic phosphate (Na(NH4)HPo4,4H2 0) was next 

 analyzed. The amount of phosphoric oxide in the salt was 

 found by igniting it and weighing the sodic metaphosphate. 

 (1 ) 1 -4650 grms. gave -6172 grms. NaPO, = 29-32 p. c. P^Os 



By the alumina process the following results were then ou- 

 tained. 



(1 ) 1-5405 grms. gave -4514 grms. P.Os = 29-30 p. c. 



(2) 1-2610 " •' -3707 » " =29-39 " 



(3) 11355 " « -3321 " " =29-29 " 



Mean 29-33. 



Calcic phosphate did not give good results by this V'^'^flZ 



account of the difficulty of washing out the calcic suipa^^ 



formed. I succeeded no better with ammonio-magnesic p ^^ 



phate doubtless because some of the magnesia went down 



