SCHWEIZER'S REAGENT AND " EAU CELESTE."' By H. Baubigny." Eau celeste" is obtained by dissolving copper salts in ammonia, and contains salts of the
type CuSO4,4NHS -f- H2O. Schweizer's reagent is prepared by treating cupric hydroxide with ammonia, and contains the base CuO,4NHs -}- 4H2O, isolated
by Malaguti and Sarzeau. Both solutions deposit cupric hydroxide when largely diluted. "Eau celeste," contains salts of the base which exists in the
free state in Schweizer's reagent. It follows that solutions of basic cupric salts should behave as mixtures of " eau celeste" and Schweizer's
reagent, and this is found to be the case. Such solutions dissolve cellulose more readily the more basic the salt. Conversely, the addition of an
ammonium salt to Schweizer's reagent partially converts it into "eau celeste," and if the former has previously been saturated with cellulose, the
cellulose is precipitated as the ammonium salt is added. This change is produced by ammonium carbonate and by carbonic anhydride, and it follows,
therefore, that when Schweizer's reagent is exposed to the air it will form cuprammonium carbonate, and will eventually be converted into "eau
celeste."The old method of preparing Schweizer's reagent by dissolving copper in ammonia in presence of air, is defective, since it does not avoid the
presence of carbonic anhydride, and hence gives a product •with diminished solvent powers. Potassium sulphate and sodium chloride are not decomposed
by ammonia nor by the cuprammonium base, and therefore they do not affect the properties of Schweizer's reagent. The addition of potassium or sodium
hydroxide to "eau celeste" produces a liquid which is capable of dissolving cellulose.The best method of preparing Schweizer's reagent is to
precipitate a solution of copper sulphate with the calculated quantity of soda and dissolve the hydroxide in ammonia.There can be little doubt that
the Schweizer's reagent distributed over vines, as a preventative of mildew, will be rapidly transformed into " eau celeste," which is the actual
preservative. The more easily p r i ; " eau celeste" can, therefore, be used for this puq>ose instead of the Schweizer's reagent.1 Compt. rend,
civ, 1616-1618.—Reprinted from Jour. Client. Soc., Sept. 1887. |
