1905.] 



The Use of Lime. 



403 



stone, the Great Oolite and the Portland Limestone are usually 

 of high purity, but many of the Magnesian Limestones contain 

 as much as 40 per cent, or over of carbonate of magnesia. There 

 are usually considerable variations in the purity of limestone 

 beds in the same quarry, and it is very desirable that only the 

 purest of these should be burnt for agricultural lime. Most 

 of the beds of Magnesian Limestone in Durham contain 

 large amounts of magnesia, but there are beds of limestone-- 

 usually those which are hard and grey — in most quarries of 

 Magnesian Limestone in that county which are very free from 

 magnesia, and would make good agricultural lime. 



Ground lime. — This is simply lime (lime shells) which is 

 ground to a fine powder. This is more expensive than lime, 

 as the grinding usually costs about 6s. a ton, and as bagging is 

 necessary, there is an additional charge of about 3s. a ton for bags. 

 Owing to the tendency of the lime to absorb moisture and the 

 consequent swelling, the bags generally burst so that they cannot 

 be again used. The cost of grinding could be reduced to 3s. a ton 

 or under, if the output could be materially increased. Ground 

 lime should contain not less than 85 per cent, of lime (CaO), but 

 very much now sold contains far less than this. One sample 

 examined has been found to contain under 50 per cent, of 

 lime (CaO) and over 22 per cent, of magnesia ; another 

 contained nearly 10 per cent, of unburned limestone, while about 

 25 per cent, of the lime had become slaked, and there was 

 under 50 per cent, of lime (CaO) in the sample.* Dr. Voelcker 

 states that "it is not infrequently found to be of inferior quality," 

 and gives an analysis showing more than 20 per cent, of stone 

 in a sample received by him.f There is reason to suspect that 

 some of the lime that has become slaked into a fine powder 

 at the limekiln may occasionally find its way into the bags of 

 ground lime. The amount of slaked lime found in some samples 

 cannot all be accounted for by the slaking that may take place 

 between the limekiln and the farm. A good sample may cost 

 about 1 8s. a ton at the limekiln. The cost might be reduced, 

 as already indicated, if the demand were greater and if the 

 railway companies would carry it at the same rate as ordinary 



* Analysis by Mr. Collins, 



t R.A.S.E, Journal, Vol. LXV., p. 255. 



K K 2 



