MEETING REPORT
Society for Analytical Chemistry 46th meeting of the Physical Methods Group, Society for Analytical Chemistry, was held jointly with the Liverpool a n d Xorthwestern Section of the Royal Institute of Chemistry at Preston, Lancs., on May 28. HE
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Twin-Beam Null-Point Fluorimeter. STRETCH, C. D. E. E., Porton, Wilts.
J. P. DOWDALL ASD
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The instrument is used to assess quantitatively small amounts of fluorescent substanres in solution. I t consists of a tungsten lamp light source with suitable filters, and two photomultipliers having their dynode loads connected in a bridge circuit. One load resistor is variable and is provided with a precision dial, and a galvanometer is arranged to indicate balance of the bridge. One photomultiplier is illuminated by the fluorescent light, the other by a controlled quantity of filtered light from the lamp. The variable resistor in the final dynode of the control photomultiplier is used to restore balance in the bridge. The instrument is calibrated with known weights of fluorescent material, and will accurately measure 1 X gram of fluorescein and 1 X lo-’ gram of riboflavin. Quenching of the Fluorescence of Traces of Uranium in Fuzed Sodium Fluoride by Iron and Plutonium. G. N. WALTON, A.E.R.E., Harwell, Nr. Didcot, Herts. The quenching effect of iron and plutonium at various concentrations on the fluorescence of traces of uranium in fuzed sodium fluoride illuminated by ultraviolet light was reported. The transmission of the fuzed melts for ultraviolet light has also been measured at different wave lengths. This shows that sodium fluoride alone, and also when containing traces of iron sufficient to cause quenching, has no absorption bands. Sodium fluoride containing uranium has a wide absorption band in the ultraviolet. The fluorescent spectrum of uranium also does not change appreciably in the presence of iron in amounts sufficient to cause high quenching. The results can be interpreted by Merritt’s and Forster’s theories of energy transfer, &s it is assumed energy can be transferred over distances of the order of 100 A-speculative in view of uncertainties associated with transmission of light in a diffusing medium.
nizes the stimulatory effects of suxamethonium or acetylcholine. The reactions of the frog’s rectus abdominis preparation t o these neuromuscular blocking agents have been investigated in order to provide a method for the bioassay of each drug. These methods exhibit reasonably narrow limits of error and may be used to estimate small quantities of drug.
At a meeting of the h-orth of England Section on April 10, t h e subject discussed was the Food and Drugs (Amendment) Bill, t o amend the Food and Drugs Act, 1938, and the Food and Drugs (Milk and Dairies and Artificial Cream) . k t , 19.50. T. W. Lovett, chairman, reviewed t h e salient features of the bill, followed by discussion. On June 21, E. Green, 15 Cpper Sutton Lane, Heston, Hounslow, Middlesex, England, gave a n account of the history of cosmetics and discussed in particular the analytical approach t o characterization of cosmetic products. A special meeting of the society was held July 21 at the Royal Institution, London, to discuss the use of perchloric acid in analytical chemistry. Perchloric Acid and Some Organic Perchlorates. HAROLD BL-RP. F. G. PRAILL, Queen Elizabeth College, Campden Hill Road, London W.8. TON ASD
The action of perchloric acid and some organic perchlorates on various types of organic compounds-e.g., anhydrides and etherswas discussed with particular reference to the formation of, especially, the alkyl perchlorates and related compounds. The simple alkyl esters of perchloric acid have long been known to be highly explosive: in the free state they possess many of the properties of covalent compounds. Consequently, when experiments that can lead t o their formation are carried out, the risk of serious explosion is always present.
A Bomb in a Test Tube. Perchloric Acid Idiosyncrasies. G . FREDERICK SMITH,University of Illinois, Urbana, Ill. Wet-oxidation procedures making use of hot concentrated perchloric acid were demonstrated. Three specific types of reaction shown involved the “liquid fire reaction” as applied to the rapid destruction of oxalic acid, chromacized catgut tissues, and chrometanned leather in analytical procedures for the destruction of the first substance, and for the recovery and determination of chromium from the latter two materials. The dual roles of perchloric acid as a nonoxidizing reagent and as The summer meeting of the Biological Methods Group was an exceptionally strongly oxidizing agent were illustrated by suitable held June 16 at the Sational Institute for Research in Dairying, experiments. The use of perchloric acid solutions of cerium(1V) as stoichiometric oxidation media for the quantitative determination of Shinfield, Berks. aliphatic organic compounds was demonstrated. It was shown that perchloric acid has the general properties of a superior solvent. The Estimation of Depolarizing Substances by Use of the Isolated Semispinalis Ceruicis Muscle of the Chick. K. J. CHILDASD E L E ~ S O R stability of metallic perchlorates was contrasted experimentally with the corresponding instability of chlorates. The reactions of perchloric J. ZAIMIS,School of Pharmacy, University of London, London. acid with cellulose, wool, sulfur, and coal were demonstrated. The semispinalis cervicis muscle of the chick, like the rectus abdominis muscle of the frog, responds by contracture to acetylcholine and to substances possessing an acetylcholinelike action at the neuromuscular junction. This muscle offers advantages over the rectus ahdominis of the frog because the relaxation following the contracture is much more rapid and because it is more sensitive to substances mimicking acetylcholine. Substances such as decamethonium, succinylcholine, and adipylcholine have been used in testing this method. The muscle of a 3- to 10-day-old chick is removed under ether anesthesia and is suspended in a 5-ml. bath of oxygenated Tyrode solution a t 40.5’ C. The onset of contracture follows almost immediately upon the addition of the depolarizing drug t o the fluid of the bath and reaches its maximum in less than 1 minute. Low concentrations of decamethonium (0.1 y per ml.), succinylcholine (0.1 y per ml.), and SIR: On occasion we have found low recoveries of sulfur when adipylcholine (0.2 y per ml.) may readily be estimated. The muscle determined by t h e methylene blue method of Johnson and Kishita remains in a state of contracture until washed with fresh Tyrode solu[Johnson, C. & and !I, Sishita, , H., A x . 4 ~CHEM., . 24, 736 (1952)]. tion, when relaxation is both rapid and complete. Doses may be adInvestigation showed t h a t the distilled water used in the preparaministered every 4 minutes for periods u p to 2 hours without any decrease in the sensitivity of the muscle. The response of the muscle to tion of the wash solution and t h e zinc acetate absorbing solution acetylcholine is irregular, but following the administration of an sometimes contained as much as 0.1 p.p.m. of copper. Under anti-cholinesterase substance a response may be obtained to 0.1 y . these conditions sulfide is quantitatively precipitated in t h e wash The response of the muscle to decamethonium may be blocked by solution and the zinc acetate solution a n a is not available t o form the previous administration of d-turbocurarine or hexamethonium, and concentrations of d-tubocurarine of 1 y can be detected. methylene blue. Copprr in the sample or in the digestion miuture is without effect on the determination. Use of the Frog’s Rectis Abdominis for Assay of Laudexium and We recommend t h a t distilled water prepared b y distillation Allen & Suxamethonium. G . B. CHESHERAND H. 0. J. COLLIER, from an all-glass still and containing less than 10 p.p.m. copper be Hanbury’s,Ltd., Ware, Herts. used in t h e preparation of reagents for this sulfur determination. Two neuromuscular blocking agents used in anesthesia affect in C. M. JOHSSOS differentways the frog’s rectus abdominis muscle preparation in vitro. University of California Suxamethonium stimulates its contracture, while laudexium antagoT. H. ARKLEY Berkeley 4, Calif.
CORRESPONDENCE
Microestimation of Sulfur in Plant Materials, Soils, and Irrigation Waters
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