Sulphomolybdic solution

Sodium Chloride To 2 ml of a 20% w/v soln. of NaCl in C02-free DW, add sufficient DW to make 100 ml. To 100 ml of this soln. add 4 ml of sulphomolybdic solution, shake, add 0.1 ml of dilute tin(II) chloride solution, allow to stand for 10 minutes and examine 20 ml of the resulting solution. Any colour produced is not more intense than that produced in 20 ml of a soln. obtained by treating a mixture of 2 ml of phsphate standard solution (= 5 ppm P04) and 98 ml DW in the same manner. 

Sulphomolybdic Solution Dissolve with heating, 25 ml ammonium molybdate in 200 ml DW. Separately, with care, add 280 ml H2S04 to 500 ml DW. Cool and mix the two solutions and dilute to 1 Litre with DW. 

To 100 ml of the soluhon prepared (neutralized as prescribed if necessary), 4 ml of sulphomolybdic reagent R3 is added. The solution is shaken and 0.1 ml of stannous chloride solution R1 is added. A standard is prepared in the same manner using 2 ml of phosphate standard solution (5 ppm PO ) R and 98 ml of water R. After 10 min, compare the colors using 20 ml of each soluhon. Any color in the test soluhon should not be more intense than that in the standard. 

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