THE REVIVAL OF INORGANIC CHEMISTRY. 301 



the constitutional formulas of inorganic compounds. The more con- 

 servative organic chemists have always been careful to stare that the 

 so-called structural formulas are reaction formulas merely; that is, that 

 they are not intended to express the actual relations of the atoms 

 in the molecule, but are merely convenient schemes for rendering pos- 

 sible reactions visible to the eye. Probably most chemists regard them 

 as more than this, as actual diagrammatic representations of the way 

 in which the atoms are combined. The formula of marsh gas, for 

 example, 



H 



I 

 H— 0— H, 



k 



is regarded as more than a visualizing of its chemical properties; it 

 implies that the carbon atom is an actual physical link between the 

 hydrogen atoms, which are combined directly with the carbon bnt 

 not with each other. Stereochemical formulas are confessedly more 

 than reaction formulas, and the steric conception of the so-called double 

 and triple union asserts that these actually exist in the sense the words 

 imply, and are not merely names for unknown conditions. 



Many of the simpler organic structural formulas unquestionably have 

 an enormous mass of evidence in their favor, but many others we must 

 be on our guard against taking too seriously, and must for the present 

 regard as nothing more than reaction formulas. That we can regard 

 any of them as well established is due, more than to anything else, 

 to the almost invariably constant tetravalency of the carbon atom. 

 Unfortunately, the valency of many of the elements entering into the 

 composition of inorganic compounds appears to be extremely variable 

 and uncertain, and this has greatly impeded the study of the structure 

 of these bodies. The inorganic chemist has been far too prone to 

 assume that the structural theories of the organic chemist are of uni- 

 versal applicability, and, having once for all attributed a certain 

 valency to an element, has been often content with devising structural 

 formulas which have no better claim to recognition than that all the 

 so-assumed bonds are "satisfied." At other times a particular valency 

 has been assumed for no other reason than that it enabled him to con- 

 trive a formula for the special case under consideration. The books 

 treating of such matters frequently exhibit wonderfully ingenious inor- 

 ganic structural formulas which are wholly devoid of a reasonable 

 amount of experimental evidence and which are, therefore, often noth- 

 ing but pure rubbish. With many inorganic chemists, formula worship 

 has degenerated into fetishism. Let us consider a few examples. For 

 nitric acid, one of the simplest and most familiar inorganic compounds, 

 several constitutional formulas may be written, in which the hydrogen 

 is directly united to the nitrogen or separated from it by one or two 



