146 



CHEMISTRY. 



tic ether, and again of iodide of ethyle on the 

 product first obtained. They do not decide at 

 present whether the acids having the formula 

 of butyric acid are identical, or only isomeric. 

 These facts, thus briefly recorded, convey but 

 meagre hints of what is being done in the way 

 of the synthetic production and the transfor- 

 mations of organic bodies and their products. 



Acetic and Caproic Acids. Some time since, 

 M. Harnitz-Harnitzsky effected the synthesis 

 of benzoic acid, by reaction of chloro-carbonic 

 acid with benzole. He has more recently 

 (Comptes Rendus, May 1, 1865) extended the 

 method to the series of hydrocarbons homolo- 

 gous with marsh-gas; and he has thus arti- 

 ficially prepared acetic acid, and its homo- 

 logue, caproic acid. For the first-named of 

 these, marsh-gas being passed along with chlo- 

 rocarbonic acid into a vessel heated to 120, a 

 reaction occurs, in which the two former give 

 place to chloride of acetyle and chlorhydric 

 acid: thus, C 2 H 4 + 0,0,01,, =C4H 3 3 C1 + H.C1. 

 The greater part of the chloride of acetyle 

 being collected in a vessel connected with 

 the receiver, and which contained caustic soda 

 [in solution, it appears; though one account 

 speaks of addition of water only, making no 

 mention of the alkali], the final result was an 

 acetate of soda, fr.om which the acetic acid is 

 of course readily separable. So, the oxychlo- 

 ride of carbon (chlorocarbonic acid) with hy- 

 dride of amyle, Ci Hi 2 , furnished chloride of 

 caproyle and chlorhydric acid, from the for- 

 mer of which caproic acid was ultimately ob- 

 tained. 



Substitutions among Alcohol- Radicals, in 

 their Compounds. "VVe can in this place barely 

 refer to two interesting papers, by 0. Friedel 

 and J. M. Crafts jointly, given in the Amer. 

 Jour, of Science, July, 1865 the first entitled, 

 " On the Replacement of one Alcoholic Radical 

 by another in Compounds of the Ether Class ; " 

 and the second, " On Etherification." As an ex- 

 ample of the results obtained by the authors, it 

 was found that a mixture of acetate of ethyle 

 and amylic alcohol, heated for 48 hours to 

 about 250 0., and distilled, gave acetate of 

 amyle and common alcohol ; while, upon heat- 

 ing in like manner and distilling a mixture of 

 the two latter bodies (time given, 40 hours, and 

 temperature 240) the reverse change to acetate 

 of ethyle and amylic alcohol occurred. 



IV. PHYSICO-CHEMICAL PHENOMENA AND 

 PRINCIPLES. In connection with the notices of 

 certain interesting phenomena to be given under 

 this head, and of which latter some are men- 

 tioned for the first time in this work, will be 

 included also the statement of such applications 

 as in each case have been suggested or actually 

 carried into effect. (See also the separate arti- 

 cle, DIALYSIS.) 



Permeability of Heated Metals to Gases. 

 MM. Deville and Troost first proved the fact 

 of permeability of metals at an elevated tem- 

 perature to gases, by showing the passage, 

 under such circumstances, of the gas, hydrogen, 



through the pores of a white-hot platinum 

 tube. In one form of these experiments, tubes 

 of hammered and of cast platinum (^th inch 

 thick, in one case) were fitted by means of 

 corks into the axis of a shorter and wider tube 

 of glazed porcelain ; a slow current of pure and 

 dry hydrogen was then maintained through the 

 porcelain tube, whilst a current of dry air was 

 transmitted through the platinum tube. At 

 ordinary temperatures no change was observed 

 in either gas. But upon gradually heating the 

 porcelain tube in a furnace when the temper- 

 ature reached about 2,000 F. the oxygen con- 

 tained in the air had entirely disappeared, and 

 from the platinum tube there escaped only ni- 

 trogen, mingled with steam. The hydrogen 

 must, therefore, have passed through the pores 

 of the platinum, and combined with the oxygen 

 of the air, generating the water-vapor. At 

 temperatures still higher, nitrogen, vapor, and 

 hydrogen were delivered ; and upon gradually 

 cooling, the several phenomena appeared in 

 inverse order. 



With a drawn tube of soft steel, thickness 3 

 to 4 milimetres, the same fact has been more 

 recently established in another manner. This 

 tube was suitably fixed within a larger one 

 of porcelain, heated as before, and was made 

 to receive at one end a stream of hydrogen, 

 while at the other it communicated only with a 

 glass tube 80 centimetres in height, and dipping 

 below into a mercury bath. A stream of hy- 

 drogen was thrown into the heated apparatus 

 for 8 or 10 hours. Upon then suddenly arrest- 

 ing this, the mercury rose on the instant to 

 740 mm., nearly the usual barometrical height. 

 This showed a nearly complete vacuum to exist 

 at once within the porcelain tube ; and proved 

 the escape of the hydrogen through the pores 

 of the steel tube. 



It has been suggested accordingly, that an 

 iron tube introduced into a furnace where there 

 are reducing gases would serve to carry off tho 

 hydrogen ; and also, that air-pyrometers with 

 iron or platinum bulbs cannot be relied on to 

 measure very high temperatures ; though glazed 

 porcelain, it appears, would confine the gases 

 completely. 



The passage of gases into heated metals has 

 been shown in a different manner by M. Caillo- 

 tet ; and tho phenomena of gaseous diffusion, 

 so ably investigated some years since by Mr. 

 Graham, have been studied in the new direc- 

 tion in which M. Deville's experiments above 

 detailed point, by M. Matteucci and by M. 

 Stanislas Meunier. 



Dissociation of Elements of Compound Bodies 

 ~by Ifcat.Fof^& brief notice of this subject, 

 see CHEMISTHY, ANNUAL CYCLOPAEDIA, 1863. 

 M. II. Sainte-Claire Deville has continued his 

 researches in connection with this singular 

 phenomenon, and has had several brief papers 

 detailing his results published. In most of 

 these researches his apparatus was essentially 

 4;he same with that described in the notice re- 

 ferred to, and also above. 



