CORRESPONDENCE EXPLOSION HAZARDS FROM THE USE OF ISOPROPYL AND OTHER ETHERS To the Editor DEARSIR: In the August issue ( I ) , isopropyl ether was recommended as a suitable extraction medium. Subsequently, the author has had his attention called to correspondence by Morgan and Pickard (2) in which they cite two explosions which resulted from the use of this solvent. each case the ether had stood for a period of five or six years and peroxides had accumulated. Quoting from their article, Diisopropyl ether had been employed t o extract small wantities of organic acids from an aqueous solution, and after drying, about 50 cc. of the extract was distilled with the aid of an electric heater. After practically all the ether had passed over white fumes were noticed and the heater was switched off. A few moments later the explosion occurred and the worker received numerous glass fragments in the hands and face but sustained no serious injury although onelens of his spectacles was shattered into fragments and the other was pitted.. I t is abundantly evident that the greatest care should be exercised in every operation involving the application of diisopropyl ether. The inference may be drawn that freshly prepared diisopropyl ether can be distilled from a water bath without danger, but that, on keeping, it is liable to develop quantities of peroxides and to become dangerous.. . Old specimens and those of d ~ b t f uage l should never he used unless they fail to liberate iodine from aqueous potassium iodide.
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This warning against the use of aged ethers is extended by Williams (3) as follows: AU ethers which we have studied have been found t o form peroxides upon storage, and with practically all, explosions have been experienced. D i e t h ~ l ethyl , tertiary buty& ethyl tertiary amyl, and diisopropyl ether are w r y hazardous.. Diethyl ether is well known to form explosive peroxides.. Danger occurs whenever an ether is dry distilled, usually toward the end of the distillation as the peroxide concentration increases. How fsr one can go with the distillation depends upon the amount of peroxide present. mechanical shock increases the likelihood of explosion, No should be dry distilled unless peroxides have been proved absent. Even a trace of peroxide may be dangerous since it becomes concentrated in the still residues. Peroxides are determined by adding acidified alcoholic potassium iodide and titrating the liberated iodine with thiosulfate. Peroxides are destroyed by treatment with ferrous sulfate, sodium bisulfite, acidified potassium iodide, or sodium sulfite. The latter reacts more slowly and less completely than the others. When the peroxide content is high, treatment may evolve considerable heat and the reagent should be added slowly and with cooling.. . . The development of peroxides during storage may he considerably retarded by the addition of oxidation inhibitors. Suitable inhibitors are diphenylamine, rr-naphthol. Snaphthol, and hydroquinone.. . . Approximately 0.05% of the inhibitor is added. Though these inhibitors are effective in reducing peroxide formation to perhaps one hundredth of that which would be formed without an inhibitor, it is advisable not t o trust them implicitly but always to test for peroxides and destroy them if found before distillation, and then, if convenient, to distil the ether with steam:
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upontesting our stock of ethers, it was found that they all contained traces to appreciable amounts of
peroxides. Butyl ether which had been in stock a little over a year gave a very positive test for peroxides. Our Store Room Department has arranged, therefore, to label all ether bottles as follows: BEFORE USING
test this ether far explosive peroxides by shaking 1 cc. with an equal volume of a 2% solution of potassium iodide which has been slightly acidified. If iodine is liberated, purify before using. For purification, add one volume of 25% sodium hydroxide to 200 volumes of ether and steam-distil. The peroxides will be the aqueous and should be poured down the drain. Test the distillate before using t o insure the absence of Peroxides are formed when ether is permitted stand in contact with air, and should be tested for periodically. ,
ISOP~OPY~ ether which gave a decided test for peroxides failed to indicate the presence of peroxides after being subjected to the treatment prescribed above. T~ the writerrs knowledge, no explosions have oc"lTed in regu1ar instructional laboratories from the Use of ethers in extractions. This is doubtless due to the facts that dry distillations are seldom, if ever, resorted to in the usual laboratory preparations, and supply rooms do not sufficient amounts of ethers to permit them to age on the shelves long enough to become dangerous. Because of these facts, perhaps, the current laboratory manuals to give adequate, if any* warning to the possible presence of peroxides in ethers and the attendant dangers. Gattermann and Wieland (a), on the that: When evaporating large amounts of impure ether which has been exposed to air for a long time, the possihility of the occmence of a violent explosion a t the end of the evaporation, due to the presence of peroxides, must be taken into account. Such ether has a pungent odor, and liberates iodine from an acid solution of iodide, The can be destroyed by shakimg with a weakly acid solution of ferrous sulfate.
Perhaps ovff-emphasis has been placed on the fk hazard involved in the use of ethyl and other lowboiling ethers, and insacient warning has been given relative to the coedstent hazard (5), Cordially yours, E. F. DEGERING PURDUE
UNIVERSlTl
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INDIANA
E., F., "The (I) D E G E R ~ O of aniline." J. CKEM. E ~ u c . ,13, 377-8 (Aug., 1936). (2) MORGAN,G. T. AND P I ~ D R., H.. "Explosions arising from diisopropyl ether," J . Chnn. Industry. 55, 421 (May 22, 1936). See also Ind. Eng. Chem.,N m s Ed.. 14, 305 (Aug. 10, 1936). (3) WILLIAMS, E. C., J. Sac. Chm.Ind., 55,580-1 (July 17,1936). (4) G A ~ E R M A NAND N WIGLAND.''Laboratory methods of organic chemistry," The Macmillan Co., 1Q32,p. 107. (5) Cf.I&. Eng. chnn., N W ~~ d . 14, , 305 (AUZ.10, 1936).
