202 



DETERMINATION OE PlIOSPHOEIC OXIDE. 



The figures given iiuder (i) below are lliose found, while 

 those given under (ii) are calculated for 



11 XTI3 . 2 r.Os . 52 M0O3 . 36 H3O :— 



We are therefore justified in assigning the above formula to 

 the Lorenz ammonium iihospho-molybdato precipitate. 



This compound requires, according to the equation: 



3 (NHJaPO, .^ (NHJ^HPO, . 52 M0O3 + IOI Ts^aOIT + aq. 



= 4 (T^H,),Hr(), + (NH,),MoO, + NH,NaMoO, 



+ 50Na3IoO^ + aq., 



one hundred and one moLs. of sodium hydroxide for two mols. 

 of phosphoric oxide, i.e., i^equires a ratio 

 XaOH : P.Os = 505 : 1, 



instead of 50 : 1, as found by experiment. AVe are at 

 present unable to account satisfactorily for the discrepancy. 

 The following experiments coufiiTa fhe' composition found. 

 If by the addition of formaldehyde the ammonia be con- 

 verted into hexamethylenetetramine, the amount of sodium 

 hydroxide used to neutralise the precipitate with respect to 

 phenolphthalein should correspond to the equation : 



2 r,0, . 52 M0O3+ 112 K'aOH 



= 4 Xa,HPO,-f52 Na2MoO, + 54 H,0. 



Precipitates piepared from similar quantities of phosphoric 

 oxide were dissolved in sodium hydroxide, with and without 

 the addition of formaldehyde, and the excess of sodium 

 hydroxide determined in the usual way, Avith the following 

 results : — - 



(a). 



N/10 NaOH required 



for standard 



method. 



N/10 NaOH required 



after adding 



CH,0. 



* Mean of several determinations. 



