in the buret. (The column is re- 

 charged after each third sample 

 is passed through by washing with 

 150 ml. of 3N hydrochloric acid 

 and rinsing with 150 ml. of freshly 

 boiled and cooled distilled water). 



Procedure : Dippel, Bricker, and 

 Fur man (1954) reported that in flame 

 analysis "at the lower phosphate con- 

 centrations, the emission intensity of 

 calcium varies linearly and inversely 

 with the phosphate concentration." This 

 is the basis used for the determina- 

 tion of phosphorus pentoxide. A cation 

 exchange resin is used to remove inter- 

 fering cations. 



Weigh between 0.5 and 1.0 gm. of 

 dried sample into a 150-ml. beaker 

 and add 10 ml. of 6N hydrochloric acid 

 and 5 ml. of concentrated nitric acid. 

 Heat at medium setting on an electric 

 hot plate until evaporation is complete, 

 bake for 10 minutes, allow to cool, and 

 add 2 ml. of 6N hydrochloric acid and 

 10 ml. of distilled water. Heat to near 

 boiling and filter the mixture using a 

 medium-flow filter paper (we used 

 Whatman No. 4 filter paper), letting 

 the filtrate flow directly into the cation 

 exchange column, and catch the effluent 

 in a 100-ml. volumetric flask. Wash 

 the filter and column with freshly 

 boiled and cooled distilled water until 

 about 80 ml. of effluent is collected 

 in the flask. Pipette 10 ml. of calcium 

 oxide solution into the volumetric flask 

 and fill to the mark with distilled water. 

 Add 10 ml. of calcium oxide solution 

 to each of a set of standards containing 

 concentrations of 0, 100, 200, 300 and 

 400 p. p.m. of phosphorus pentoxide in 

 100-ml. volumetric flasks. 



Measure emission intensities for 

 each sample as follows: unknown, dis- 

 tilled water, standard judged to be 

 below unknown, distilled water, stand- 

 ard judged to be above unknown, and 

 distilled water (the value obtained for 

 distilled water is subtracted from the 

 value obtained for each unknown and 

 each standard) using a Beckman Model 

 DU spectrophotometer equipped with 

 photomultiplie r and oxy -acetylene 

 flame attachments. Spectrophotometer 

 settings as follows: Photomultiplie r - 



set to null dark current; sensitivity 

 control - about midpoint; wavelength - 

 554 m mu; selector switch - 0.1; 

 phototube resistor - 2000 megohn^s; 

 slit width - adjust to zero meter needle 

 on p. p.m. phosphorus pentoxide 

 standard at 100 percent emission; 

 acetylene pressure - 3.5 p.s.i.; oxygen 

 pressure - 9-5 p.s.i. Bracket the net 

 emission of the unknown by reading the 

 appropriate pair of standards from the 

 prepared series of standards imme- 

 diately after reading the unknown. Re- 

 port the concentration as percent 

 phosphorus pentoxide on dry weight 

 basis. 



Strontium 



Reagents and Apparatus : 



1. 6N hydrochloric acid (HCl) - equal 

 volumes of concentrated hydro- 

 chloric acid and distilled water. 



2. 3N hydrochloric acid (HCl) - 1 

 volume of concentrated hydro- 

 chloric acid to 3 volumes of dis- 

 tilled water. 



3. Concentrated nitric acid (HNO^). 



4. Strontium (Sr) standard solution 

 (1000 p.p.m.) - dissolve 1.6849 

 gms. of strontium carbonate 

 (SrC03) in 10 ml. of 6N hydro- 

 chloric acid. Filter, using rapid- 

 flow filter paper, letting filtrate 

 pass through a column of amber - 

 lite IRA 400 (OH) and catching the 

 effluent in a 1 -liter volumetric 

 flask. Rinse the column well with 

 freshly boiled distilled water, add 

 washings to the 1 -liter flask, and 

 fill to mark with distilled water. 



5. Strontium (Sr) standard solution 

 (200 p.p.m.) - dilute 200 ml. of 

 strontium standard solution (1000 

 p.p.m.) to 1 liter with distilled 

 water. 



6. Amberlite IRA 400 (OH) - anion 

 exchange resin (manufactured by 

 Rohm and Haas Connpany). 



7. Anion exchange column - the col- 

 umn is made by placing a plug of 



11 



