CH. XXXVI. LIEBIG— ORGANIC CHEMISTRY. 377 



HO,Na* tells us that one atom of each of these substances, 

 weighing respectively, i, 16, 23, form a molecule of soda. 

 And thus a complete chemical language has sprung up, by 

 which chemists in all parts of the world can understand at 

 once what is the composition of any substance; and by 

 means of these simple letters the most complicated chemical 

 problems can be worked out clearly and intelligibly. 



Dalton's theory was received very quickly by chemists, 

 considering how entirely new the ideas were which it 

 taught. His friend Dr. Thomson, an eminent chemist 

 (born 1773, died 1852), gave a very clear account of it in 

 his * System of Chemistry,' and brought it under the notice 

 of Davy and Faraday ; and a great French chemist, Gay- 

 Lussac (born 1778, died 1850), adopted it at once, and 

 added another discovery in favour of it in 1809 — namely, 

 that when substances are reduced to gas, and the gas is 

 collected, it is found that the different elements combine in 

 equal or multiple volumes. 



You will understand this by turning back to the com- 

 pounds of nitrogen and oxygen (p. 373), where you will see 

 that there was always either i, 2, 3, 4, or 5 volumes of 

 oxygen collected for one of nitrogen, and never a part 

 of a volume. This was really a different fact from the one 

 Dalton pointed out, that the elements combine in definite 

 weights, and it was necessary to complete the law of mul- 

 tiple proportions. 



Liebig the Great Teacher in Organic Chemistry.— And 

 now, before closing the history of chemistry, we must mention, 

 in passing, one great division of the science of which we 

 cannot attempt to give any real account — namely, the science 



» Na stands for Natrium, the Latin name for soda, now used for 

 the metal sodium. 



