US2720544A - Ether preservation - Google Patents

Description

United States Patent Ofiice 2,720,544 Patented Oct. 11, 1955 ETHER PRESERVATION Edward Mallinckrodt, Jr., St. Louis, and Archie E. Ruehle, Kirkwood, Mo., assignors to Maliinckrodt Chemical Works, St. Louis, Mo., a corporation of Missouri No Drawing. Application July 19, 1954, Serial No. 444,391

11 Claims. (Cl. 260-6115) This invention relates to ether preservation, and more particularly to the preservation of ether by means of certain dithizone preservative compounds.

Briefly, this invention relates to a composition com prising ether and a preservative compound selected from the group consisting of dithizone, cupric dithizonate, lead dithizonate and stannous dithizonate. The invention also relates to the method of preserving ether which comprises dissolving therein a preservative compound selected from the above-noted group.

Among the objects of the invention may be noted the provision of improved means of preserving ether against decomposition; the provision of such means which are efiective in minute quantities to preserve ether; and the provision of means of the character described which preserve ether for relatively long periods of time. Other objects and features will be in part apparent and in part pointed out hereinafter.

The inventionaccordingly comprises the products and methods hereinafter described, the scope of the invention being indicated in the following claims.

Diethyl ether in untreated tin cans, within a short time following its manufacture, may acquire sufficient decomposition products to make it fail to pass the United States Pharmacopoeias rigorous requirements for ether intended for anesthesia. In recognition of these properties of ether, the Pharmacopoeia requires that ether for anesthesia be packed in tight containers of not more than 3 kg. capacity and that it be used within twenty-four hours after removal from the original container. Peroxide and aldehyde impurities are particularly objectionable in anesthetic ether, and indeed are limited to the merest traces by the specification of the United States Pharmacopoeia. Once started, the formation of peroxides may increase through auto-oxidation. Heat, light, air and catalytically active surfaces inside the container influence the formation of ether peroxides. The eifects of these factors on the formation of peroxide impurities may be considerably minimized by forming on the cans inner surface an adherent layer of tin oxide or a coating of metallic copper. Such expedients, however, are not entirely satisfactory. The best results have been obtained with a container having a copper-tin oxide coating on the inside surface, as described and claimed in our U. S. Patent No. 2,587,744, issued March 4, 1952. Another expedient which has been employed is the addition of a preservative to the ether which prevents or inhibits peroxide formation. Hydroquinone and diphenylamine are well-known preservatives; but these compounds possess only limited usefulness.

In accordance with the present invention, dithizone (diphenylthiocarbazone) and certain dithizonate metal organic complexes have been found which exhibit an improved preserving action on ether. When dissolved in ether in minute amounts, they are effective in preventing, inhibiting or delaying the formation of peroxides, thereby prolonging the keeping time of ether following manufacture. The use of these preservative compounds in conjunction with treated or coated containers, such as mentioned above, is particularly advantageous and considerably increases the stability of ether in storage. In addition to dithizone, the particular dithizonate salts which have been found effective in preserving ether are the cupric, lead and stannous salts.

These dithizone preservative compounds of this invention are more effective than hydroquinone to increase the keeping time of ether even at concentrations onetenth to one-hundredth that of hydroquinone. All the compounds of the present invention exhibit improved preserving action at a concentration of only 10- molar or less when compared with hydroquinone at ten times this concentration (IO- molar). Furthermore, when employed in conjunction with treated containers having an interior adherent coating of copper-tin oxide or lacquer varnish, still smaller concentrations of these preservative compounds are efiective.

The following examples illustrate the invention.

Example 1 The preservative action of these compounds upon ether was demonstrated by an accelerated aging test of the compositions of the present invention under conditions which favor the rapid spoilage of ether, i. e., contact with a polished tin surface and shaking it at a temperature of F. for sixteen hours. The preservatives to be tested were dissolved in freshly distilled anhydrous (absolute) ether, initially containing less than 0.05 p. p. m. peroxide and less than 2-3 p. p. m. aldehyde, and made up to the desired concentration. By this test, the relative effectiveness of various preservatives and other methods of preserving ether can be determined.

At the end of the sixteen-hour test period the ether was tested for the amount of peroxide and aldehyde it contained. If the sample was found to contain more than 0.2 part per million peroxide (the U. S. P. limit corresponds to about 0.5 p. p. m.) or over 3 p. p. m. aldehyde as acetaldehyde (the U. S. P. limit corresponds to slightly over 13 p. p. In.) it was considered to have failed in the test. In carrying out the tests, the preservative is added to 18 ml. of freshly distilled ether in a tin vessel half full, the inner surfaces of which have been mildly abraded to remove surface film or tarnish, and the vessels shaken 16 hours at a temperature of 100 F. The well-known ammonium thiocyanate-ferrous sulphate reaction was used with a set of standard colors to determine the peroxides, and Nesslers reagent with color standards was used to estimate the aldehyde.

In the case of hydroquinone, it was found that, at a concentration of 10* molar (ll mg./l.), twenty out of twenty-one samples passed the accelerated aging test with respect to peroxide, whereas, at a concentration of 10- molar 1.1 mg./l.) only ten out of fifty-two samples passed. The color test for aldehyde could not be read at 10* molar because hydroquinone at this concentration interferes with the test; but at a concentration of 10* molar nearly half of the samples failed. In each series of tests, samples of ether containing no preservatives were included to be certain that the conditions were such that untreated ether would spoil during the sixteenhour test period.

Three samples of ether containing diphenylamine at a concentration of 10" molar (1.7 mg./l.) and three samples containing the same compound at a concentration of 10 molar (0.17 rug/l.) were also prepared and tested. All six samples failed both the peroxide and aldehyde tests.

Three samples of ether containing dithizone at a concentration of 10* molar (2.56 mg./l.), nine at 10 molar (0.256 mg./l.) and twelve at 10- molar 3 (0.0256 mg./l.) were tested by the above procedure. At the end of the accelerated aging test it was found that all samples at a concentration of 10 and lO molar passed both the aldehyde and peroxide tests, while at a concentration of molar six samples passed the aldehyde and peroxide tests.

Example 2 Example 1 was repeated except that three samples of ether containing cupric dithizonate at a concentration of 5X10 molar (2.86 mg./l.) and six samples at a concentration of 5x10 molar (0.286 mg./l.) Were employed. At both these concentrations, all samples passed both the aldehyde and peroxide tests.

Example 3 Example 1 was repeated except that three samples of ether containing lead dithizonate at a concentration of 5 10- molar (3.58 mg./l.) were employed. All sam plcs passed both the aldehyde and peroxide tests.

Example 4 Example 1 was repeated except that three samples of ether containing stannous dithizonate at a concentration of 5X10 molar (3.13 mg./l.) were employed. All samples passed both the aldehyde and peroxide tests.

Thus, the ether preservatives of the present invention when tested according to the accelerated aging tests are many times (e. g., ten to one hundred) more efiective in preserving ether than hydroquinone as determined by standards higher than those required by the U. S. Pharmacopoeia. Moreover, when the preservative compounds of this invention are employed in conjunction with treated containers such as a copper-tin oxide coated can, for example, concentrations even smaller than those used in the foregoing examples are efiective to preserve ether for extended periods of time.

In view of the 'above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

4. A composition comprising ether and lead dithizonate.

5. A composition comprising ether and stannous dithizonate.

6. The method of preserving ether which comprises dissolving therein a compound selected from the group consisting of dithizone, cupric dithizonate, lead dithizonate and stannous dithizonate.

7. The method of preservingether which comprises confining in an air-tight container ether having dissolved therein a compound selected from the group consisting of dithizone, cupric dithizonate, lead dithizonate and stannous dithizonate.

8. The method of preserving ether which comprises confining in an air-tight container. ether having dissolved therein dithizone.

9. The method of preserving ether which comprises confining in an air-tight container ether having dissolved therein cupric dithizonate.

10. The method of preserving ether which comprises confining in an air-tight container ether having dissolved therein lead dithizonate.

11. The method of preserving ether which comprises confining in an air-tight container ether having dissolved therein stannous dithizonate.

No references cited.

Claims (1)

1. A COMPOSITION COMPRISING ETHER AND A PRESEVATIVE COMPOUND SELECTED FROM THE GROUP CONSISTING OF DITHIZONE, CUPRIC DITHIZONATE, LEAD DITHIZONATE AND STANNOUS DITHIZONATE.