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ANALYTICAL CHEMISTRY
believe t h a t application of the operating rule in most actual cases will prove preferable to guessing a t i limits or to operating witho u t them. The operating rule has no theoretical foundation. 4. We define “accurate method” by the following example. If a sample (either standard or unknown) contains 50% chlorine on the basis of the most recent table of atomic weights, then an analytical method for chlorine is accurate if it yields a chlorine content practically indistinguishable from 50% as the mean of a large number of determinations. According to this definition, accuracy is a n operational concept independent of the estimated standard deviation of the analytical method. 5 . We are glad that Dr. Wernimont has pointed out specifically the uncertainties inherent in s, the estimated standard deviation. We consider t h a t a bias of 5% in s may be neglected in guaranteeing the result of a single determination. We recommend t h a t the “running adjustment of s” be made over all the relevant results available so as to reduce, not only such bias, but uncertainties arising from the “random sampling distribution of sJ as well. 6. We agree that the operating rule provides only for a risks, but we do not believe t h a t p risks need be considered if the analytical method is accurate by the definition above. Of course,
actual situations may involve both a and p risks. We agree that no simple rule can be formulated when both risks are present, and we can only fall back on the third sentence under 3 above. 7. Comment 5 of the paper did not make clear that the requirement “if n is very large” applies to the Camp-Meidell inequality as well as to the normal distribution. In both cases, the chances given of falling outside 3s limits are strictly valid when n is large enough to make s and u practically identical. 8. Dr. Wernimont evidently believes, as do we, that blind application of the operating rule is hazardous-in cases, for example, where replication has been unsatisfactory or the sample is not representative. There is unfortunately no substitute for judgment. We have attempted to guard against trouble by making the limits ( & 39) generous, and we repeat that the rule ought not to be applied R hen the data suffice for rigorous statistical treatment. H. A. LIEBH.4FSKY E. W. BALIS
H. G PFEIFFER
‘
Research Laboratory General Electrlc Co. Schenectady, K. I-.
Society of Public Analysts T THE
i 9 t h annual general meeting of the Society of Public
A Analysts and Other Analytical Chemists, held in London on
LIarch 6, the following officers were elected: president, D. 17‘. Kent-Jones; past presidents serving on council, Lewis Eynon, G. IT. Monier-Williams, J. R. IYicholls, George Taylor; vice presidents, .4. J. Amos, T . lIcLachlan, Eric Voelcker; honorary treasurer, J. H. Hamence; honorary secretary, IC A. \T’illiams: other Adams, S . L. .4llport, h.L. Bacharach, members of council, C. 1. R. C. Chirnside, B. S. Cooper, 11. Corner, D. C. Garratt, S. Heron, H . W. Hodgson, H. 31. IS. H. Irving, H. E. Monk, H . C. S. de Whalley; ex-officio members, T. W. Lovett, chairman of S o r t h of England Section; R. S. Watson, chairman of Scottish Section; A. YI. Waid, chairman of llicrochemistry Group; J. Haslam, chairman of Physical Methods Group; H. 0. J. Collier, chairman of Biological Methods Group. J. R. Sicholls, retiring president, delivered an address on ”Public Health Hazards and the ;Inalptical Chemist.” The ninth annual general meeting of the hlicrochemistry Group was held on January 29 in London. The following officers were elected: chairman, A. M. Ward; vice chairman, G. F. Hodsman; hon. secretary, D. F. Phillips, 101 South Promenade, St. Annes-on-Sea, Lytham St. Annes, Lancs.; and treasurer, G. Ingram. The retiring chairman, Cecil L. Wilson, addressed the meeting on “Microchemistry, an Appraisal.” At the 18th annual general meeting of the Scottish Section held in Glasgow January 28, the following officers were elected: chairman, R. S. T a t s o n , vice chairman, F. J. Elliott; hon. secretary and treasurer, J. A Eggleston, Boot’s Pure Drug Co.. Ltd., h l o t h e r a d St., Airdrie, Lanarkshire. A t a meeting held in Edinburgh April 30 a paper on “Modern Methods of Analysis in the Training of the Student” was presented by Christina C. Miller. At the 28th annual general meeting of the North of England Section held in Manchester on January 31, the following officers were elected: chairman, T. W. Lovett; vice chairman, J . R. Walmsley ; hon. secretary and treasurer, Arnold Lees, 87 Marshside Road, Southport, Lams A. A. D. Comrie gave an address on “Beer Foam.” At a meeting of the society organized by the Physical Methods Group, and held January 30 in Birmingham, the following papers were presented and discussed:
Chromatography Past and Present. TREVOR I. WILLIAMS. Far from being a modern discovery, chromatography, with the exception of ion exchange chromatography, has been applied in many different fields of chemistry for at least a century. That it has been widely used only during the past 15 years may he attributed to the fact that only comparatively recently have many problems arisen for which chromatography has unique advantages over older and well established methods. Inorganic paper chromatography was intensively studied by Runge about 1850 and many of his original chromatograms are still extant. In the nineteenth century he was followed by Schoenbein and Goppelsroeder, and in the early twentieth century by Grnss. Modern interest, however, stems from the work of Martin and Synge. The originators of adsorption chromatography were Day, Albrecht and Engler, and Tswett, though as early as 1850 the soil chemists Thompson and Way were perfectly familiar with the separations that occur on columns of adsorbent. Modern interest stems from the application of the method in the carotenoid field initiated by Lederer and Kuhn. Ion exchange chromatography was developed during the last war, when it proved of immense value for isolating the tiny quantities of fission products resulting from the various atomic projects; it also revolutionized the chemistry of the rare earths. There are now few fields of chemical analysis in which chromatography in one of its three principal forms has not proved equal or superior to conventional methods. In the inorganic field an alternative to conventional group analyses has been found in paper chromatography. I n organic analyses it has proved especially valuable in examining complex natural products, such as food and drink, in which unidentifiable constituents often interfere with normal tests. In the biochemical and medical field chromatography has been used in the analysis of such diverse substances as vitamins, hormones, antibiotics drugs, and alkaloids; especially important is the application to urine analysis. The ready availability of radioactive isotopes has proved an important development, particularly i n paper chromatography. Chromatography in the gas phase has proved very valuable in the inert gas field, but undoubtedly much progress can be made here: indeed, this is perhaps the most promising field for future progress. Inorganic Chromatography on Cellulose.
Quantitative Separation D. B. REES-EVANS
of Rhodium, Palladjum, Iridium, and Platinum.
R . 4.WELLS. The separation of the platinum metals has hitherto involved a complicated procedure of precipitation, solution, and reprecipitation. A new method utilizes the principles of partition chromatography in obtaining a quantitative separation of rhodium, iridium, platinum, and palladium. The process, which employs cellulose as the adsorbent and organic solvents as eluting agents, is relatively speedy and is capable of reducing the concentration of one metal in another from 50 t o + O . O O l % , in one operation. When dealing with a mixture of all four metals, a solution of the sodium chloro- salts is freshly prepared in chlorine water and the platinum, palladium, and iridium are AND
