settings as follows: Photomultiplier - 

 set to null dark current; sensitivity 

 control - clockwise extreme; wave 

 length - 403.3 m mu; selector switch - 

 0.1; phototube resistor - 2000 megohms; 

 slit width - adjust to zero meter needle 

 on 400 p. p.m. manganese dioxide at 

 100 percent transmission; acetylene 

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

 9.3 p.s.i. Bracket the net emission of 

 the unknown by reading the appropriate 

 pair of standards from the prepared 

 series of standards immediately after 

 reading the unknown. Report concen- 

 tration as percent manganous oxide on 

 dry weight basis. (We first determined 

 percent manganese dioxide, but subse- 

 quently found percent manganous oxide 

 would be a more useful expression.) 



Magnesium oxide and potassium oxide 



Reagents : 



1. 6N hydrochloric acid (HCl) -equal 

 volumes of concentrated hydro- 

 chloric acid and distilled water. 



2. Concentrated nitric acid {HNO3). 



3. Magnesium oxide (MgO) standard 

 solution (2000 p. p.m.) - weigh 

 2.0000 gms. of ovendried (UOOC.) 

 magnesium oxide into a 400 -ml. 

 beaker. Dissolve in a minimum 

 volume of 6N hydrochloric acid, 

 transfer to a 1 -liter volumetric 

 flask, and fill to mark with dis- 

 tilled water. 



4. Potassium oxide (K^O) standard 

 solution (1000 p. p.m.) - weigh 

 1.5828 gms. of ovendried (110° C) 

 potassium chloride into a 1 -liter 

 volumetric flask, dissolve and 

 dilute to 1 liter with distilled 

 water. 



5. Aluminum oxide (AI2O3) standard 

 solution (4000 p. p.m.) - dissolve 

 in distilled water 4.4500 gms. of 

 alum inum amm onium sulfate 

 [Al2(S04)3.(NH4)2S04.24H20] and 

 dilute to 250 ml. with distilled 

 water. 



6. Ferric oxide (Fe203) standard 

 solution (2000 p. p.m.) - dissolve 



1.0000 gm. of oven dried (110° C.) 

 ferric oxide in 30 ml. of 6Nhydro- 

 chloric acid and dilute to 500 ml. 

 with distilled water. 



7. Manganese dioxide (Mn02) stand- 

 ard solution (500 p. p.m.) - place 

 0.2500 gm. of oven dried (110° C.) 

 manganese dioxide in 20 ml. of 

 6N hydrochloric acid, heat until 

 dissolved and dilute to 500 ml. 

 with distilled water. 



8. Calcium oxide (CaO) standard solu- 

 tion (10,000 p. p.m.) - dissolve 

 4.4617 gfms. of calcium carbonate 

 (CaC03) in 20 ml. of 6N hydro- 

 chloric acid and dilute to 250 ml. 

 with distilled water. 



9. Phosphorus pentoxide (P2O5) 

 standard solution (500 p. p.m.) - 

 dissolve 0.5000 gm. of anhydrous 

 dibasic phosphate (Na2HP04) in 

 carbon dioxide (CO2) free distilled 

 water and allow to flow through a 

 cation exchange column. Catch 

 effluent in a 500-ml. volumetric 

 flask and dilute to 500 ml. with 

 distilled water. 



Procedure : We have used the basic 

 system for the determinations of mag- 

 nesium and potassium in bottom sedi- 

 ments as reported by Roy (1956). 



Weigh 1.0 gm. of dried sample into 

 a 150-ml. beaker and add 10 ml. of 6N 

 hydrochloric acid and 5 ml. of con- 

 centrated nitric acid. Heat at medium 

 setting on an electric hot plate until 

 evaporation is complete, bake for 10 

 minutes, allow to cool, 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) catching the filtrate in a 100-ml. 

 volumetric flask. Fill to mark with 

 distilled water and use for determining 

 magnesium oxide and potassium oxide. 

 To each of a series of six 100-nnl. 

 volumetric flasks, add 5 ml. of the 4000 

 p. p.m. aluminum oxide standard, 25 

 ml. of the 2000 p. p.m. ferric oxide 

 standard, 2 ml. of the 500 p.p.m. 

 manganese dioxide standard, 7 ml. 

 of the 10,000 p.p.m. calcium oxide 



