THE ASSAY OF SUGAR HOUSE PRODUCTS. 



residue is apparently dry ; take up with hot water, filter and wash till free of 

 chlorides; dry, ignite, and weigh the residue 8i0 2 . 



Insoluble Silica. Mix the residue obtained in the determination of the 

 sand with four or five times its weight of fusion mixture, composed of mole- 

 cular proportions of sodium and potassium carbonates, and keep at a red heat 

 for (half an hour after effervescence has ceased ; dissolve out with dilute 

 hydrochloric acid, evaporate to dryness and determine the silica as before. 



Iron, Alumina. Mix the filtrates from the determinations of soluble and 

 insoluble silica ; evaporate to convenient bulk, add ammonia till alkaline, and 

 heat till the solution smells only faintly of ammonia ; filter while hot ; wash, 

 dry, ignite, and weigh the precipitate as Ee 2 3 -fAl 2 3 . If there be present 

 any large quantity of iron and alumina after decanting off the supernatant 

 liquid, the precipitate should be dissolved in hydrochloric acid and 

 re-precipitated. 



Lime. Precipitate the lime in the filtrate from the iron and alumina 

 while boiling hot with ammonium oxalate ; allow to stand for six hours, and 

 filter, wash, dry and ignite the precipitate to constant weight and weigh as 

 CaO ; convert the lime to sulphate or carbonate by evaporation to dryness with 

 either sulphate or carbonate of ammonia and again ignite, and weigh as 

 CaS0 4 , orasCaC0 3 ; CaC0 3 X '56 = CaO ; CaS0 4 X '4118 = CaO. 



Magnesia. Precipitate the magnesia in the filtrate from the lime determin- 

 ation as phosphate by the addition of sodium phosphate ; agitate the solution 

 violently, and allow to stand for twelve hours ; filter, wash with dilute ammonia, 

 dry, ignite strongly, and weigh as Mg 2 P 2 7 : Mg 2 P 2 7 x *3604 = Mg 0. 



As magnesia is detrimental to the value of good limestone, Geerligs has 

 given a scheme for its rapid estimation. Two grms. are dissolved in hydro- 

 chloric acid, evaporated to complete dryness, the residue brought into solution 

 with hydrochloric acid, boiled after the addition of a few drops of nitric acid, 

 and evaporated to small bulk. An excess of calcium carbonate is added to 

 precipitate iron and alumina, the precipitate filtered off, and the filtrate 

 collected in a flask to which an excess of lime water is added ; the flask is 

 filled nearly to the neck and set aside to settle ; the supernatant liquid is 

 decanted through a filter, and the precipitate washed by decantation. The 

 precipitate from the lime water contains the magnesia ; it is dissolved in 

 hydrochloric acid, the lime precipitated as before by ammonium oxalate, and 

 the magnesia determined in the filtrate. 



The method of Sundstrom for the rapid estimation of magnesia in lime- 

 stones is as follows : 



Weigh out one grm. of material into a small dish, add about 100 c.c. 

 water and 25 c.c. of normal hydrochloric acid ; heat to boiling, allow to cool 

 and titrate the excess of acid with normal caustic soda, thus obtaining the 



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