Dr. Redtenbacher on a Class of Organic Acids, 501 



than the other ; thus proving the cotton to be a more perfect 

 insulator than the silk, which has hitherto been chosen as best 

 adapted for the purpose of insulation. 



The acid employed was a mixture of equal parts of nitric 

 acid, sp. gr. 1*46, and sulphuric acid, sp. gr. 1*83, and the 

 cotton was immersed for about five minutes. It was not 

 highly explosive, detonated only partially when struck with a 

 hammer, and required to be heated considerably to cause it 

 to explode *. 



King's College, London, Yours trulv > 



November 13, 1846. J. E. BoWMAN. 



LXXI. On a Common Origin of the Acids (CH) W 4 with 

 a Boiling-point under 300° Centigrade. By Dr Joseph 

 Redtenbacher. (Translated by E. F. TESCHEMACiiER.)t 

 TNDER this head I include not merely the volatile acids 

 ^ of butter, but also acetic acid, metacetonic acid, valeri- 

 anic acid, &c. ; and, in short, all those acids, according to the 

 above formula, beginning at n == 4 to n = 20, and including 

 all the intervening members whose values are even numbers 

 of n. These are acetic acid, metacetonic acid, butyric acid, 

 valerianic acid, caproic acid, cenanthylic acid, caprylic acid, 

 pelargonic acid (a new acid, n = 18), and capric acid. 



By former examinations, it is known that they occur and 

 are formed under the most varying circumstances. They are 

 found partly in plants and in animals, in small quantities, as 

 mixtures of solid and fluid fats ; their more immediate origin 

 in these cases has not yet been clearly shown. They may be 

 produced from bodies resembling aldehyd, (CH)„ 2 , by sim- 

 ply withdrawing the oxygen. The similar theoretical origin 

 of acetic acid, metacetonic, butyric, valerianic and cenanthylic 

 acids has been already proved. That the same has not been 

 accomplished with capric, caprylic and pelargonic acids, is 

 owing to the want of a sufficient quantity for examination. It 

 is not probable that the origin would be found in the organ- 

 ism of the corresponding aldehydes. The different aldehydes 

 by decomposition have been heretofore represented by com- 

 plex atoms ; they have been produced from organic bodies, 

 but not found in them, although the possibility cannot be 

 denied that they may be formed by organic bodies. Another 



* [In agreement with the above statement, I may mention that Mr. Reeks, 

 of the Museum of Economic Geology, when drying some of the substance 

 in question, and drawing it out, heard a crackling noise, which induced him 

 to present it to the gold-leaf electrometer, when it instantly caused strong 

 divergence of the leaves. — R.P.] 



t Communicated by the Chemical Society; having been read May 18, 

 1846. 



