170 The Phosphates of America. 



MAGNESIA MIXTURE. 



Dissolve 110 grammes of dry crystallized magnesium chloride 

 and 280 grammes of ammonium chloride in one litre of distilled 

 water. Filter, add 700 c.c. liquor of ammonia of specific gravity 

 .96 and shake. Allow to cool and then add sufficient distilled 

 water to complete two litres, mix thoroughly and label. 



NEUTRAL AMMONIUM CITRATE SOLUTION. 



Mix 370 grammes of commercial citric acid with 1500 cubic 

 centimetres of water ; nearly neutralize with crushed commercial 

 carbonate of ammonia ; heat to expel the carbonic acid ; cool ; add 

 ammonia until exactly neutral (testing by saturated alcoholic 

 solution of coralline) and bring to a volume of two litres. Test the 

 gravity, which should be 1.09 at 20 C., before using. 



AMMONIUM NITRATE SOLUTION. 



Dissolve 200 grammes of commercial ammonium nitrate in 

 water and bring to a volume of two litres. 



MOLYBDIC SOLUTION. 



Dissolve 150 grammes of ammonium molybdate in one litre of 

 distilled water. Pour the solution slowly and in small portions at 

 a time into one litre of nitric acid of specific gravity 1.20. After 

 each addition of the ammonium molybdate solution the mixture 

 must be shaken and the agitation kept up until the liquid is en- 

 tirely clear. 



Keep the mixture in a warm place for several days, or until a 

 portion heated to 40 C. deposits no yellow precipitate of ammonium 

 phospho-molybdate. Decant the solution from any sediment, and 

 preserve in glass-stoppered vessels. 



Fifty c.c. of this solution suffice to precipitate 0.100 gramme 



P 2 5 . 



SATURATED SOLUTION OF AMMONIUM OXALATE. 



Place about eight ounces of pure ammonium oxalate in a litre 

 bottle, fill up with pure distilled water, shake occasionally during 

 a few hours, finally allow to settle and use the supernatant liquid, 

 drawing it off with a pipette as required. 



STANDARD POTASSIUM PERMANGANATE SOLUTION. 



For the accurate determination of iron in small quantities we 

 prefer the permanganate to any other reagent. The iron is re- 



