LIME AND CEMEJ^T INDUSTKIES 671 



Potassium dichromate 



lime is used in the manufacture of this material, as one of the 

 ingredients of the mixture containing chrome ore, alkaline salts 

 and fuel. The materials are finely ground, mixed and roasted in 

 a furnace, the object of the lime being to prevent fusion and aid 

 in the formation of insoluble chromates. The lime used for this 

 purpose has to be very finely ground to facilitate slaking, and it 

 should furthermore be as free from silica and magnesia as pos- 

 sible.'*' 



Paper manufacture^ 



Lime is used in the manufacture of paper to boil the rags in, 

 the object being to get rid of the remaining dirt in them, and 

 also to decompose some glutinous substances, which if allowed to 

 remain would injure the flexibility of the fiber. The quantity of 

 lime employed varies according to its composition and the condi- 

 tion of the rags, but ranges from 6 to 15 pounds to the 100 

 pounds of rags. 



Agricultural uses 



Lime is a very beneficial ingredient of the soil, if it is in a 

 condition to be taken up by the plants, that is in a soluble form. 

 Many soils may contain it in the form of silicate, as in feldspar, 

 but till the mineral containing it has decomposed the lime does 

 not become available. Some soils contain sufiicient lime for the 

 use of the plants, but in the case of others it has to be added 

 artificially either as an ingredient of manufactured fertilizers or 

 in the form of quicklime. 



If the lime is present in the soil in the form of carbonate of 

 lime, it can be detected by the effervescence produced on adding 

 weak acid to the soil. The quantity of lime present in the soil 

 naturally depends on the composition of the parent mass from 

 which the soil was derived, and the climate, whether dry or 

 moist ; soils in the former tending to have a much higher per- 



1 Frasch. Min. ind. 4: 101. 



2 Davis, C. T. Paper manufacture. 



