POISONS, CONTAGIONS, MIASMS. 



The gases which are formed in mines of 

 wood coal, and cause danger in their work- 

 ing, are not combustible or inflammable as 

 in mines of mineral coal ; but they consist 

 generally of carbonic acid gas, and are very 

 seldom intermixed with combustible gases. 



Wood coal from the middle bed of the 

 strata at Ringkuhl gave on analysis 65-40 

 64-01 carbon and 4-75 4'76* hydrogen ; the 

 proportion of carbon here is the same as in 

 specimens procured from greater depths, but 

 that of the hydrogen is much less. 



Wood and mineral coal are always ac- 

 companied by iron pyrites (sulphuret of 

 iron) or zinc blende (sulphuret of zinc ;) 

 which minerals are still formed from salts 

 of sulphuric acid, with iron or zinc, during 

 the putrefaction of all vegetable matter. It 

 is possible that the oxygen of the sulphates 

 in the layers of wood coal is the means by 

 which the removal of the hydrogen is 

 effected, since wood coal contains less of 

 this element than wood. 



According to the analysis of Richardson 

 and Regnault, the composition of the com- 

 bustible materials in splint coal from New- 

 castle, and can n el coal from Lancashire, 

 is expressed by the formula C24 HI 3 O. 

 When this is compared with the composition 

 of woody fibre, it appears lhat these coals 

 are formed from its elements, by the re- 

 moval of a certain quantity of carburetted 

 hydrogen and carbonic acid in the form of 

 combustible oils. The composition of both 

 of these coals is obtained by the subtraction 

 of 3 atoms of carburetted hydrogen, 3 atoms 

 of water, and 9 atoms of carbonic acid from 

 the formula of wood. 



3 atoms of carburet- 

 ted hydrogen C3 H6 



3 atoms of water H3 O3 



9 atoms of carbonic 

 acid - - C9 O18 



Mineral coal 



C36 H22 022=wood 



C12 H 9 O21 



C24 H13 O 



Carburetted hydrogen generally accom- 

 panies all mineral coal ; other varieties of 

 coal contain volatile oils which may be sepa- 

 rated by distillation with water. (Reichen- 

 bach.) The origin of naphtha is owing to 

 a similar process of decomposition. Caking 

 coal from Caresfield, near Newcastle, con- 

 tains the elements of cannel coal, minus the 

 constituents of olefiant gas C4 H4. 



The inflammable gases which stream out 

 of clefts in the strata of mineral coal, or in 

 rocks of the coal formations, always con- 

 tain carbonic acid, according to a recent 

 examination by Bischoff, and also carburet- 

 ted hydrogen, nitrogen, and olefiant gas; 

 the last of which had not been observed, 

 until its existence in these gases was pointed 

 out by Bischoff. The analysis of fire-damp 



* The analysis of brown coal from Ringkuhl, 

 as well as all those of the same substance given 

 in this work, have been executed in this labora- 

 tory by M. Kiihnert of Cassel. 



after it had been treated with caustic potash 

 showed its constituents to be, 



Gas from an. 



abandoned Gerhard's Gas from 9 



mine near passage near mine near 



Wallesweiler. Luisenthal. Lickwfge. 



Vol. Vol. Vol. 

 Light carburetted 



hydrogen 91'36 83.08 7910 



Olefiant gas 6'32 1'98 16' 11 



Nitrogen gas 2'32 14'94 4"79 



100-00 100-00 100-00 



The evolution of these gases proves that 

 changes are constantly proceeding in the 

 coal. 



It is obvious from this, that a continual 

 removal of oxygen in the form of carbonic 

 acid is effected from layers of wood coal, in 

 consequence of which the wood must ap- 

 proach gradually to the composition of 

 mineral coal. Hydrogen, on the contrary, is 

 disengaged from the constituents of mineral 

 coal in the form of a compound of carbo-hy- 

 drogen; a complete removal of all the hydro- 

 gen would convert coal into anthracite. 



The formula C36 H22 O22, which is 

 given for wood, has been chosen as the em- 

 pirical expression of the analysis, for the 

 purpose' of bringing all the transformations 

 which woody fibre is capable of undergoing 

 under one common point of view. 



Now, although the correctness of this 

 formula must be doubted, until we know 

 with certainty the true constitution of woody 

 fibre, this cannot have the smallest influence 

 on the account given of the changes to which 

 woody fibre must necessarily be subjected in 

 order to be converted into wood or mineral 

 coal. The theoretical expression refers to 

 the quantity, the empirical merely to the 

 relative proportion in which the elements of 

 a body are united. Whatever form the first 

 may assume, the empirical expression must 

 always remain unchanged. 



CHAPTER XIII. 



ON POISONS, CONTAGIONS, AND MIASMS. 



A GREAT many chemical compounds, 

 some derived from inorganic nature, and 

 others formed in animals and plants, pro- 

 duce peculiar changes or diseases in the 

 living animal organism. They destroy the 

 vital functions of individual organs; and 

 when their action attains a certain degree 

 of intensity, death is the consequence. 



The action of inorganic compounds, such 

 as acids, alkalies, metallic oxides, and salts, 

 can in most cases be easily explained. They 

 either destroy the continuity of particular 

 organs, or they enter into combination with 

 their substance. The action of sulphuric, 

 muriatic, and oxalic acids, hydrate of pot- 

 ash, and all those substances which produce 

 the direct destruction of the organs with 

 which they come into contact, may be com- 

 I >ared to a piece of iron, which can caus* 



