293] 



Determination of i Insoluble 1 Alkalis 



173 



by decantation, using 50 c.c. of water for each washing j then 

 wash once with hot water on the filter. 



The filtrate will contain all the alkalis in the form of 

 chlorides, together with some calcic chloride and calcic hydrate. 

 Precipitate the lime by adding ammonium carbonate solution 

 in excess, together with a little ammonia and ammonium 

 oxalate. Boil well and filter, washing by decantation. Evapo- 

 rate the filtrate to dryness in a large platinum dish, and ignite 

 gently to drive off all ammoniacal compounds. Weigh as 

 NaCl-f KC1, and proceed as described in paragraphs 277 and 

 278. 



ANALYSIS OF LIMESTONES 



There is very little difference in the general method 

 adopted between the analysis of limestones and the analysis of 

 the ' soluble ' portion of soils, though it is not often necessary 

 to determine any other constituents in a limestone than the 

 silicates, the lime, and the magnesia. 



293. General Table. 



Dissolve in HC1, and evaporate to dryness ; dissolve in water, and filter. 



Precipitate. 

 Dry and 

 weigh as 

 insoluble 

 silicates 

 and sand. 



Filtrate. Treat with ammonia, filter, dissolve precipi- 

 tate in HC1, and re-precipitate ; add both filtrates 

 together. 



Precipitate. 

 Weigh as 

 Fe 2 3 , A1 2 0„ 

 and P 2 5 . 

 Dissolve up 

 and esti- 



mate P 2 5 > 

 as in refuse 

 manure. 



Filtrate. 

 filter. 



Add HA, then (NH 4 ) 2 Ox ; 



Precipitate. 

 Burn and 

 weigh as 

 CaCO., 



Filtrate. Evaporate 

 with UNO,. Add 

 microcosmic salt to 

 boiling solution; cool, 

 and render ammoni- 

 acal. Weigh precipi- 

 tate as Mg 2 P 2 7 . 



