77 o THE POPULAR SCIENCE MONTHLY. 



Synthesis requires exact knowledge of all the elements and forces 

 involved in the object of its investigation, and looks to the inductive 

 or analytic method to furnish these data. There must be no unknown 

 quantities in the problem to be solved, for synthesis seeks not to build 

 from the unknown but only to re-form the known. Hence it properly 

 awaits to receive verified facts from chemical analysis, which has yet 

 been able to compass but a fractional part of the organic compounds. 



Chemical elements are the basis of chemical science ; they are 

 neither produced nor destroyed, but are the enduring and constant 

 factors in the many series of changes in the properties of matter, 

 which represent the desideratum of this science. And yet the knowl- 

 edge of molecules is very meager ; the weights of but a few are known, 

 even among the commonest elements and compounds ; and but little 

 account has been taken of atomic motion, which furnishes the most 

 perfect explanation of chemical reaction. 



Of the highly complex series of albuminoid substances, which 

 neither crystallize nor possess any combining equivalent, and therefore 

 can not be expressed by exact symbols, analytic chemistry knows but 

 little, and hence it would be in vain to attempt their reproduction by 

 synthesis. Notwithstanding our ignorance of essential facts, the prog- 

 ress of synthetic chemistry has been great, and the prospect is favor- 

 able for more brilliant achievements in the future. 



Wohler, in 1828, first, by synthesis, formed urea from ammonia 

 cyanate. It was claimed by the critics that urea, being a nitrogenous 

 metabolite, a product of animal decomposition, was a mineral, rather 

 than an element of the animal tissues ; but when Fownes, in 1841, 

 prepared cyanogen itself direct from its elements, and, from this salt, 

 urea, the fact was recognized and accepted, although it was affirmed 

 that a " vital force " was necessary to account for the more complicated 

 organic compounds, of which series urea was a member having only 

 simple combinations. This was disproved by Berthelot in 1856, when 

 he obtained the potassium salt of formic acid. Then followed the pro- 

 duction of acetylene, marsh-gas, ethylene, and other hydrocarbons, 

 from inorganic materials. Marsh-gas was converted into methyl alco- 

 hol, and ethylene into ethyl alcohol, and from these alcohols formic 

 and acetic acids were made. 



Startling as these results were, the substances formed were, rela- 

 tively, simple in nature, and the " vital force " still ruled in the more 

 complicated bodies of organic origin. 



Synthetic work continued to achieve brilliant results and added to 

 its list of vegetable compounds oxalic, valeric, malic, citric, tartaric, 

 and salicylic acids, the oils of garlic, mustard, and wintergreen, also 

 conine, alizarine, and indigo. 



Of animal compounds, leucin, creatin, sarcosin, and taurin are 

 added to the large and growing list of substances from which analysis 

 and synthesis have banished the vital force, and harmonized the facts 



