"Ludwig Mond, F. R. S., 1839-1909," : a lecture / by F.G. Donnan.

  • Frederick G. Donnan
Date:
1939
Catalogue details

Licence: In copyright

Credit: "Ludwig Mond, F. R. S., 1839-1909," : a lecture / by F.G. Donnan. Source: Wellcome Collection.

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    of various difficulties, amongst which may be mentioned the loss of ammonia, all attempts failed, until Ernest Solvay, a Belgian chemist, succeeded in overcoming a good many of the difficulties by means of new types of apparatus, and, in partner¬ ship with his brother Alfred, started business as Solvay et Cie, with a capital of £5,440. The small works which they built at Couillet, near Charleroi, began operations in 1865. Perhaps I may mention at this point that the ammonia- soda process consists essentially of the reaction (in aqueous solution) NH4HC03 + NaCl -> NaHCOg + NH4C1 Owing to its relatively low solubility, the bicarbonate of soda, NaHC03, separates as a fine crystalline precipitate, and so causes the reaction to go on. We have here a beautiful example of the principles introduced into chemical science by the great French chemist, Claude Louis Berthollet, the friend and adviser of Napoleon. Doubtless it was the influence of Berthollet which led to the pioneer investigation of Fresnel. In practice, the ammonium bicarbonate is formed by the solution in the brine of ammonia and carbon dioxide gases, so that the foregoing reaction may be written NH3 + C02 + H20 + NaCl -> NaHC03 + NH4C1 The carbon dioxide is obtained by the heating of limestone (CaC03 essentially), whilst the lime obtained in this way is used to recover the ammonia by means of the reaction CaO + 2NH4C1 -> 2NH3 + CaCl2 + H20 The total reaction may be written in the form CaC03 + C02 -j- H20 + 2NaCl -> 2NaHC03 -f- CaCl2 Ammonia acts only as an intermediate, whilst the only waste product is a solution of calcium chloride. I have written all these reactions in their simplest form, i.e., without regard to the ionic theory or the formation of carbamate. When the process is treated from the point of view of physical chemistry, it forms one of the most beautiful examples of homogeneous and heterogeneous equilibria. Ludwig Mond and John Brunner were ambitious young men. We can picture in our minds many a long evening at “The Hollies/' when the possibilities of the future were eagerly dis¬ cussed. Mond, the man of science and the already experienced chemical technician, was probably the imaginative leader in
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