238 0. /S. Piolman — Determination of Uranium and 



ashless filter papers (Schleicher & Schiill, l^o. 589), and also 

 that an asbestos felt of ordinary tightness in a Gooch crucible 

 would not entirely retain the precipitate. By shaking up the 

 flask containing the asbestos, however, allowing it to settle a 

 minute and then pouring off the particles still in suspension, 

 a very finely-divided asbestos was obtained, which, when poured 

 upon the felt made in the ordinary way, was found to give a 

 pad of such tightness that the filtrate obtained from the ammo- 

 nium uranyl phosphate was perfectly clear. The tightness of 

 the. felt, however, together with the gelatinous character of the 

 precipitate, caused the process of filtering and washing to be 

 rather slow. 



The process as worked out for the determination of the phos- 

 phoric acid was as follows : A measured amount of a standard 

 phosphate solution (containing about 4*7 grams of microcosmic 

 salt per liter) was drawn into a beaker, and a mixture of about 

 twelve grams of ammonium acetate, formed by neutralizing 

 about lO^-^^ of ammonium hydroxide (0*90 sp. gr.) with acetic 

 acid (50 per cent), and from 2 to 4°""^ of free acetic acid was 

 added. The total volume was made up to about 150'^"'' and 

 the solution heated nearly to boiling. The ammonium uranyl 

 phosphate was then precipitated by slowly adding an excess of 

 uranium nitrate, with stirring, and the precipitate was boiled 

 gently for about twenty minutes, allowed to settle, and filtered 

 on a tight felt of asbestos. The precipitating beaker and the 

 precipitate were washed thoroughly with a dilute solution of 

 ammonium acetate containing a little free acetic acid (to over- 

 come the tendency of the precipitate to pass through the filter) 

 and the crucible containing the precipitate was placed in a 

 glass funnel. Enough dilute sulphuric acid, in the ratio of 

 1 to 6, was then added to dissolve the precipitate and thor- 

 oughly wash out all the soluble uranium salt from the asbestos, 

 the solution being caught below as it passed through the cru- 

 cible and funnel in the same beaker that was used for the pre- 

 cipitation. The solution was then made up to a volume of 

 from 100 to 150°™' with dilute sulphuric acid, in the ratio of 

 1 to 6, heated to boiling, and treated just as has been described 

 for a solution of uranyl sulphate — that is, a few cubic centi- 

 meters of warm dilute sulphuric acid, in the ratio of 1 to 6, 

 were passed through the reductor and were followed by the 

 uranium solution, a few cubic centimeters more of the dilute 

 sulphuric acid, and 250°°"" of hot water. The contents of the 

 flask were then poured into a porcelain dish, diluted with 



n 

 200^^"^' of hot water, and titrated with a — solution of potas- 

 sium permanganate to a faint pink end-reaction. 



