Paper, 'On the molecular weights of the substituted ammonias. No. I. Triethylamine' by James Dewar and Alexander Scott

Description

Dewar and Scott write: 'The experiments relating to a new determination of the atomic weight of manganese recently communicated to the Society has led us to prosecute some further studies in this field of research. The following note deals with the preliminary results arrived at regarding the molecular weight of a member of a class of bodies which, strange to say, have not been previously selected for accurate determinations of this kind. The substituted ammonias are peculiarly fitted to reveal the effect of small differences from whole numbers in the conjoint values of the atomic weights of carbon and hydrogen. By selecting tertiary amines of high molecular weight it is possible to integrate these small positive or negative increments through the increase in the number of carbon and hydrogen atoms in the substituting radical. There is also a special advantage in employing the fully saturated ammonium derivatives for experiment. Theoretically it ought to be possible to ascertain by this method whether the atomic weight of hydrogen differs from unity, provided the atomic weight of carbon be accepted as sufficiently well defined, from other methods of investigation. The difficulty of getting perfectly pure substances for such work, together with the hygroscopic character of the ammonium compounds, introduces serious difficulties, and for the purpose of testing the accuracy of the proposed method, the preliminary experiments have been made with triethylamine. The triethylamine employed was made by the action of chloride of ethyl on ammonia, and was transformed into the bromide of tetraethyl-ammonium. This bromide of the fully substituted ammonium was decomposed by dry distillation into triethylamine and bromide of ethyl, and the base separated in the form of the chloride. The free base was separated from the chloride with caustic potash, and after careful drying with anhydrous oxide of potassium was subjected to fractional distillation. The portion boiling between 90° and 91° was converted into the hydrobromate and its equivalent relation to silver determined, after the method of Stas, with the following results:— Weight of salt Weight of salt Molecular weight of in vacuo. in vacuo. (C2H5) 3 N.H Br. 6.6248 ...... 3.9219 ....... 182.313 8.24088 ...... 4.8798 ....... 182.270.'

Annotations in pencil and ink.

Subject: Chemistry

Received 21 June 1883. Read 21 June 1883.

A version of this paper was published in volume 35 of the Proceedings of the Royal Society as 'On the molecular weights of the substituted ammonias. No. I. Triethylamine'.

Reference number

PP/3/32

Earliest possible date

1883

Physical description

Ink and graphite pencil on paper

Page extent

5 pages

Format

Manuscript