lie Rev, J. B. E/nmeft on the [Feb. 



This is only an approximation, an analogy which may here- 

 after lead to important results ; for the quantity of heat evolved 

 depends upon the quantities of heat contained in the bodies, 

 and the quantity remaining in the compound, which will gene- 

 rally be greater when it is a gas or liquid, than a liquid or solid. 

 The union of bases with chlorine, iodine, sulphur, and some 

 others, present analogous phenomena of combustion, and the 

 same analogy may be clearly traced. 



Since the atomic diameters of potassium and of carbon are 

 uncertain, their force is doubtful ; the former certainly is capa- 

 ble of existing in a state of much greater density than it pos- 

 sesses in its metallic state, as the great density of pure potash 

 demonstrates : the real density of carbon is also unknown ; it 

 certainly is much greater than is generally supposed ; for when 

 the lightest charcoal in fine powder, or lamp-black, is perfectly 

 mixed with water, and boiled so as to expel all the air contained 

 in the interstices, it rapidly sinks in the liquid, even if a consi- 

 derable quantity of gum, or saline matter, be contained ; yet 

 chemists state its gravity to be about 0*223. Besides, the 

 method by which the specific gravity of porous solids is usually 

 found introduces very great errors ; for by reason of capillary 

 action, the mercury employed will never enter the pores and 

 interstices of porous solids ; besides the capillary interstices of 

 all light porous solids are filled with air in a considerable state 

 of condensation, which keeps the mercury at a considerable 

 distance from contact with the solid ; even water does not readily 

 enter. When the specific gravity of a light porous solid has to 

 be taken, it should be immersed in water, or any suitable liquid 

 except mercury, and either boiled or exposed to a vacuum for 

 some time, by which means it will be freed from air : the error 

 introduced by allowing the air to remain, makes the gravity of 

 a charcoal, in reality heavier than water, only •223. 



In all analytical researches, chemical tables should be com- 

 puted for weights and magnitudes proportional to those of the 

 particles of bodies ; for in combination and decomposition, the 

 quantities are proportional to the atomic weights ; an ultimate 

 atom possesses all the properties which belong to a body, and 

 the capacity for heat is as the capacity of one particle multiplied 

 into the number of particles ; therefore the capacity of an atom 

 of any body is the real representative of the capacity of that 

 substance; the expansion of a body being caused by the separa- 

 tion of its particles, the separation which takes place between 

 two adjacent particles is the true ratio of the expansion. The 

 same may be extended to all other tables. In the following 

 table I have computed the atomic capacities of a number of 

 substances. The atomic capacity — capacity of a given weight 

 X atomic weigrht. Tlie former numbers are taken f»om Dalton's 



