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LXXII. Limited Oxidation. By J. AlfredWanklyn, Professor 

 of Chemistry at the London Institution*. 



IN writing the chemical history of an organic substance, che- 

 mists frequently assign an important place to the products 

 of oxidation, which they sometimes make use of to aid in determi- 

 ning the structure of the substance and its place in the general 

 chemical system. 



Of late years increasing attention has been paid to these oxi- 

 dation-products, which, owing to the labours of Kolbe, Berthelot, 

 Wurtz, and the researches which have been carried on in the la- 

 boratory of the London Institution, have assumed an unlooked- 

 for importance, and the study of which is so full of the promise 

 of an insight into the mysteries of chemical structure. 



Notwithstanding all this, the processes of oxidation hitherto 

 used by chemists are crude and wanting in precision — always ex- 

 cepting the grand fundamental oxidation known as " The Elemen- 

 tary Analysis }> or " Combustion," which is the very type of cer- 

 tainty and precision. 



If we refer to Limpricht's excellent Lehrbuch der organischen 

 Chemie, 1862, p. 118, we find that when alcohol is distilled with 

 bichromate of potash and dilute sulphuric acid, or with peroxide 

 of manganese and dilute sulphuric acid, it gives aldehyde, acetic 

 acid, formic acid, acetic ether, and acetal. We read moreover 

 that when the oxidation of alcohol is effected by means of nitric 

 acid in the. cold, glyoxal, glyoxylic acid, glycolic acid, oxalic acid, 

 acetic acid, and formic acid figure as oxidation -products. In 

 fact, the prevalent idea of the oxidation-process, as was well ex- 

 pressed by an eminent chemist on a recent occasion at the Che- 

 mical Society, is, that by applying the oxidizing agent one obtains 

 certain proximate products which undergo a gradual breaking 

 up as the oxidation proceeds, giving products of less and less 

 complexity, until the final result is carbonic acid and water. 



The attitude taken by chemists towards the oxidation-pro- 

 cess was illustrated by myself in 1863, when, in the progress of 

 the research on the hexyl group, working in conjunction with 

 Erlenmeyer, the observation was made that beta-hexyl alcohol gave 

 acids of less complexity than caproic acid. Before I could attach 

 much value to the result, I took care to assure myself that there 

 was no caproic acid produced and then destroyed by the further 

 action of the dilute chromic acid. I took the beta-hexyl alcohol, and 

 distilled rapidly with bichromate of potash and dilute sulphuric 

 acid, taking care that the oxidation was incomplete, and that an 

 oil distilled over along with an aqueous layer of liquid. Potash 

 was added to the oil and the aqueous layer. That portion of the 

 oil insoluble in potash was then put back and oxidized afresh, and 

 so the assurance was attained that, if caproic acid were formed and 

 * Communicated by the Author. 



