AGRlCULTUkAL LlME 145 



the amount of insoluble matter noted ; if large, it should 

 be estimated. 



Magnesia is tested for qualitatively, and if present in 

 large amount must be determined quantitatively. Good 

 agricultural limestone or lime should contain very little 

 magnesia. 



138. Lime, 



{a) Qtiicklime. — Examined qualitatively, it should 

 be white, swell considerably on slaking, and fall into a 

 fine powder. Grey limes which do not swell and which 

 slake badly are less valuable for agricultural purposes. 



The lime should be examined for insoluble matter 

 and magnesia, as in 137. 



{b) Slaked Lime. — This material should be in a fine 

 state of subdivision and free from grit, insoluble matter, 

 and much magnesia. 



139. Analysis of Agricultural Limes, 



The most satisfactory method ol analysing a lime 

 which is comparatively free from magnesia and may 

 contain quicklime, slaked lime, and carbonate, is as 

 follows : — 



{a) Insoluble Matter. — Two or 3 grams are dissolved 

 in HCl, the insoluble material filtered off, and weighed. 



{b) Carbonate. — Estimated by any of the usual 

 methods (36 {b), p. 57, or 75, p. 94). 



{c) Total Calcium. — Estimated in the usual manner 

 by precipitation as oxalate and weighing as CaO (83, 

 p. lOl). 



{d) Lime. — The lime present as oxide or hydrate 

 (quick or slaked lime) is obtained by difference from 

 the total calcium, calculated as CaO, and the carbonate 

 also calculated back from CaCOg to CaO. 



