and it is impossible by ordinary examination to discriminate 

 between the various offerings. 



(2) Few among our farmers understand the special qualities 

 and adaptations of the different kinds of lime, and few therefore 

 would be able to select wisely even were the composition defi- 

 nitely known. 



The fertilizer law now before the Legislature will help remove 

 the first of these sources of uncertainty, for under it dealers will 

 be required to guarantee composition. This bulletin, it is hoped, 

 will prove helpful in the diffusion of such knowledge concerning 

 the various kinds of lime as will enable fanners to correctly esti- 

 mate their relative values for different purposes. 



An effort has been made to procure samples of all lime products 

 that are being offered for sale in the Massachusetts markets and 

 on subsequent pages will be found the composition and cost 

 of the various products. The following states are represented: 

 Maine, Vennont, Massachusetts, Rhode Island, Connecticut, 

 New Jersey and Pennsylvania. 



3. CHEMISTRY OF DIFFERENT FORMS OF LIME. 



Lime occurs in nature as lime carbonate and in this form is 

 widely distributed as limestone, marble, chalk and marl; also 

 in the fomi of lime sulfate or gypsum. It likewise occurs as 

 phosphate of lime in bones and mineral phosphates and as car- 

 bonate in oyster shells and wood ashes. 



Limestone. — Most of the lime used in agriculture comes origin- 

 ally from limestone rock (calcite) or carbonate of lime (CaCQs). 

 Many limestones are composed partly of lime carbonate together 

 with varying proportions of carbonate of magnesia (MgCQs) (20 to 

 40 per cent) . Such mixtures are termed dolomitic limestones, and 

 their behavior is not greatly unlike the pure lime compounds. 

 Caustic magnesia does not slake or take on water as readily as 

 causticlime, and thereis reason to believe that it is more mild in its 

 action in the soil. In this country, as abroad, it has frequently 

 not met with as high favor as the high calcium limes. It is not 

 advisable to apply magnesium limestones to soils already rich in 

 magnesia and deficient in lime. Pure limestone or calcium car- 

 bonate contains some 56 parts of calcium oxide (CaO). Many 

 limestones contain from 50 to 53 per cent of calcium oxide and 

 40 per cent and over of carbonic acid, together with varying propor- 

 tions of magnesia*, iron, alumina and sand. When limestone is 

 used on the soil it should be finely ground so that the larger part 

 of it will pass a 75 mesh sieve; in other words, its beneficial action 

 will depend largely upon its degree of fineness. It is easy to see 

 a very fine limestone can be more evenly distributed and more 



*High magnesium limes should not be used for spraying. 



