H2W rOBK - i \ i i MUSEUM 



Lithographing 



raphie lir i Bomewhat impure, very fino and 



[ned limestone. It is aol only rare but valuable. The 



requirements are sufficient porosity to absorb ink and softness 



permit working with an engraver's tooL A ?ery great 



*v is undesirable. The stone Bhould also be free 



fror of impuriti 



ief Bupply thus far baa come from Solenhofen, Bavaria 

 Qthern France. It has been reported from various local- 

 in this country but never from New York state. 



Lime 



AY hen limestone is burned, that is when it is raised to a red 

 tj it is dissociated into lime oxid and carbonic acid thus. 



CaOO, = CaO + C0 2 



lim. or lime oxid carbonic acid gas 



lime carbonate quick lime carbon dioxid 



caustic lime 



The carbonic acid gas passes off and the oxid of lime remains 

 behind as a p<»wdery or lumpy substance, which is often white, 

 but may be more or less colored if iron is present. 



As limestone varies in composition, the lime will also, but the 

 <• of impurities in the lime will be nearly twice what 

 they were in the limestone, for the latter has lost 44$ of car- 

 bonic acid gas. 



T ire limestone consists of 56.^ of oxid of lime (CaO) and 1 M 



i cid. The change from carbonate of lime to oxid 



lime occur- during the burning, the carbonic acid being driven 



at a higher temperature, and in this process the lime lo 



about J b< by weight: but, as it is generally in a Bomewhat moist 



ion when it is put into the kiln, due to water in its po: 



be -till greater than that mentioned above. 

 The ] moisture in limestone is very variable and 



depends the hardness and density of the rock. The 



I orous it will be and the lower will 



