I-YD USTRIAL A S D ELVGIhTEERISGCHEMISTRY
760
the development of pharmacy, probably for the very good reason that this was impossible in a volume of such a limited size. The chronological table will be of considerable value to the student of contemporaneous history. One finds, however, comparatively few references t o pharmacy itself, and many references to events in the history of medicine and science generally which have a t best a decidedly remote bearing on the development of pharmacy. For example, one wonders what effect the passage of the first Meat Inspection Act in Germany in 1875 or the institution of the School of Mines a t Columbia University in 1864 have to do with pharmacy. The bibliography will be of considerable value to any student of pharmaceutical history or the history of allied sciences. While it cannot be claimed that the author has written a thorough history of pharmacy, he has presented a very readable and interesting outline which will occupy in the field of history of pharmacy a place comparable t o that occupied by Wells’s “Outline of History” in the field of world history. Undoubtedly, this book will create a greater appreciation of the part that pharmacy has played in the development of medicine and chemistry, and i t may act as a stimulus to others interested in the
Vol. 19, 90.6
history of pharmacy t o develop volumes which will portray in greater detail each one of the periods which LaWall has pictured to us so entertainingly.
How to Apply for a Position. By Letter and Interview. MAURICEH. WESEEN. 73 pages. Lincoln, Neb., 1927. Price, 50 cents.
BY College Book Store,
The author of this booklet, associate professor of business English a t the University of Nebraska, has given a very good analysis of the problem which confronts anyone who applies for a position, whether in person or by correspondence. Most of the space is devoted to suggestions on writing letters of application. The average letter writer, whether seeking a position or not, could profit by reading it, and those who are interested in the more practical side will find many helpful suggeqtions in the numerous examples of letters written by men seeking employment. Perhaps the most useful pages are those devoted to “Application Don’t’s’’ and “Application Do’s.” Altogether, the book should find its proper niche in business literature.
NOTES AND CORRESPONDENCE Successive Potentiometric Titration of Copper and Iron in Metallurgical Products Edztor of Indiistrial and Engineering Chemastry: I n their article under this title,’ the authors maintain that the potentiometric estimation of copper according to Zintl and Wattenberg’ gives irregular results with marked positive and negative errors up to 6 per cent. The method of Zintl and Wattenberg is as follows:
The copper solution, containing 4 t o 8 per cent free hydrochloric acid, is reduced with excess titanous chloride solution, the concentration of which need not be known, and is then titrated potentiometrically with potassium bromate or dichromate. During the titration the oxygen must be carefully excluded by passing carbon dioxide through the vessel. The oxidizing agent first oxidizes only the excess of titanous chloride, then a potential jump is noticed, which indicates the beginning of the oxidation of cuprous to cupric salt. A second potential jump indicates the end point. The solution used between the two jumps corresponds to the copper present. Buehrer and Schupp usually find their values much too low. They do not exclude atmospheric oxygen by passing in an indifferent gas, but cover the solution with kerosene. On different occasions we have also tried to work under a layer of kerosene or toluene, to protect from oxidation a solution to be titrated, but without success.a Even if the layer of kerosene is several inches thick and the stirring is slow, atmospheric oxygen penetrates through i t and, for example, in the titration of hot cupric salt solutions with titanous chloride, especially near the end point, the potential never becomes constant. If one waits long enough, titanous chloride can be added ad lib. without reaching a n end point. A second source of error is also noticeable if the tip of the buret dips only into the protective layer. The drops of the titrating liquid leaving the buret often remain for a long time inside the kerosene layer before penetrating into the aqueous solution, and if these are not noticed large errors may result. For this reason we have avoided the use of a liquid protective layer and perhaps the poor results of Buehrer and Schupp may be thus explained. Buehrer and Schupp conclude from their results that the 1 Buehrer and Schupp. THIS JOURNAL, 18, 121 (1926).
*
Bey., 55, 3366 (1922). a See also Hempel, ”Gasanalyt. Methoden,” p. 33, Braunschweig, 1913.
reduction of cupric salt by titanous chloride must be incomplete in hydrochloric acid solution, in agreement with the fact that the normal potentials of Cu++/Cu+(0.17 volt) and T i + + + + / T i + + + (0.00 volt) lie near together. This conclusion is erroneous. The difference between normal potentials indicates the possibility of titration only when no appreciable complex formation takes place in the solution.4 A complex ion is formed, however, in the case of cuprous salt in hydrochloric acid solution. The potential of a cupric-cuprous electrode is markedly shifted to the positive side by chloride. A solution of cupric and cuprous salts in equal proportions in 5 per cent hydrochloric acid gives a potential of about 0.49 volt against the hydrogen electrode, whereas in chloride-free solution the normal potential should be 0.17 volt. That the reduction of cupric salt in 5 per cent hydrochloric acid is complete with titanous chloride is seen from the fact that during titration a t the first jump one drop of the titrating solution shifts the potential at least 58 millivolts-i. e., increases the concentration of the cupric ions tenfold. The statement of Buehrer and Schupp that Zintl and Wattenberg found direct titration of cupric salt with titanous chloride impossible is entirely erroneous. Zintl and Rauch5 have not only used the direct titration for estimating copper, but also for standardizing titanous chloride. E. ZINTL BAVERACADUMY OF SCIENCES MONCHEN, GERMANY
..............
Editor of Industrial and Engineering Chemistry: In reply to the comments of Professor Zintl, it may be pointed out, first, that the writers rigorously excluded ogygen, not only by means of a layer of kerosene 1 to 2 inches deep, but also by the use of purified nitrogen bubbled through the solution. The nitrogen would be equally as effective in preventing oxidation of cuprous ion as carbon dioxide, and the kerosene we have also found very satisfactory in other titrations. Since the solutions were titrated hot, not only would the solubility of oxygen be less in the kerosene, but the kerosene vapors constantly rising would tend to prevent access of air to the protecting layer. The difficulty of enclosed droplets of solution in the kerosene layer was avoided by having the tip of the buret extend through the 4 Zintl, “Elektrometrische Massanalyse, Handbuch der Arbeitsmethoden in der anorganischen Chemie, Vol. 11, p. 984. 6 Z. anorg. Chem., 146, 281 (1925): Zintl, I b i d . 152 35 (1926).
June. 192i
I S D C S T R I S L 9-YD E,VGIiVEERISG CHE-UISTRY
76 1
kerosene layer and well into the solution. Furthermore, the its use by the University of Wisconsin. We merely call attention stirring by even rapid rotation of a glass rod a s a rule did not to the patent features t o guard against the manufacture of such agitate the layer appreciably, so t h a t suction of air into the equipment for sale or for generalIuse-by others. W. H. SCOTT solution was not able t o occur. It is very significant t h a t our results were in most cases too low, whereas if atmospheric oxidaTHE DURIRONCOMPANY,INC. DAYTON, OHIO tion of the cuprous ion formed had occurred the results would March 23, 1927 have been high. We therefore believed ourselves t o be justified in the conclusion t h a t the low results were due to incomplete reduction of the copper. The second question concerns the Cu’/Cu++ potential, and Professor Zintl’s point here is well taken. No doubt both the potentials shift greatly Cu+/Cu++ and the Ti + +/Ti + I n THIS JOURNAL, 19, 4 (1927), R. T . Haslam and R.1. W. with change in concentration of H + and C1-. Granting t h a t the Boyer, in discussing the radiation from luminous flames, mention potential difference is sufficient to warrant the conclusion that a scheme proposed by Lent [U’urme, 49, 145 (1926)l t o increase the reaction would go t o completion, we must recognize t h a t the radiation from relatively nonluminous flames by adding an the copper is largely in the form of the chloro-complex ion, which illuminating agent t o the gas so as to produce particles of carbon is known to react very slowly with certain ions, and this may t o serve as radiation centers. also be true of its reaction with titanous ion. It is probably a A similar proposal was made and tried out in 1913 by Walter question of speed as well as of equilibrium in this titration. Our A. Schmidt, of the m‘estern Precipitation Company, with the experiments have not given evidence t h a t the reaction goes to cooperation of Buckner Speed. These gentlemen had been completion under the conditions of the titration. puzzled as to why the heat requirement for portland cement The last point relates t o the direct titration of cupric ion burning was greater when oil was used as a fuel than when with titanous chloride. We regret the error on page 124 of our powdered coal was so used. They suspected that when powpaper, in which we state t h a t “Zintl and Wattenberg2 find t h a t dered coal was used, the ash particles remaining enhanced direct titration cannot be made.” These authors did not reradiation from such flames and that the absence of similar port any work on the direct titration, b u t only on the inparticles in the flame from oil might cause the lower efficiencl-. direct determination-namely, by adding excess titanous chloA series of tests was consequently undertaken a t the plant ride and titrating back with either dichromate or bromate. of the Riverside Portland Cement Company t o investigate Kolthoff reported that direct titration with titanous chloride this point. In these tests very fine dust was blown into the alone does not give accurate results for copper. Since our obserfront part of the kiln so as to mix with the combustion gases, vations confirmed those of Kolthoff and since the reference t o and the output and fuel consumption of the kiln, with and Zintl and Rauch,5 which ProFessor Zintl quotes, was unknown t o without such added dust, were noted. us a t the time our paper was accepted for publication, we The results of these tests were inconclusive, which, however, naturally assumed t h a t Zintl’s results for the direct titration were is not surprising in view of the well-known uncertainties about in agreement with ours. Further work will be done in this kiln production in the ordiuary plant and the unduly large laboratory to clarify this question. excess of fuel which always is used in connection u-ith cement T. F. I~UEHRER USIVERSITYOF ARIZOKA burning. It might be expected, however, that as the art of 0. E. SCHUPP, JR. T U C S O N , ARI.7. cement burning is improved and the fuel consumption approaches April 18, 1927 more nearly the theoretical limit, it will be possible t o demon6 Rec. luau. chim., 43, 320 (1924;. strate t h a t one actually can improve the efficiency of an oilfired kiln by some such means
Note on the Radiation from Luminous Flames
Kjeldahl Digestion Apparatus Editor of Industrial and Engineering Chemistry: We have read, with much interest, the article by E. G. Hastings, E. B. Fred, and TV. H. Peterson [THISJOURNAL, 19, 397 (1927)] with reference t o a Kjeldahl digestion shelf being operated in the laboratory of the Department of Agricultural Chemistry of the Kniversity of Ti‘isconsin, Madison, \Vis. The idea of a fume tube with nipples on the side that go into the neck of a Kjeldahl flask and some means for furnishing a positive draft, such as an exhaust fan, was patented in September, 1924, and assigned to The Duriron Company, who have since been making up and marketing them. The first Duriron tubes were made and installed a year or more before application was made for patent papers. Duriron proved so very satisfactory for the construction of these tubes and exhaust fans, gas ducts, etc., that a complete digestion shelf was designed including not only the tubes, exhaust fan, exhaust pipe, and condensate removers, but supporting frames, burners, etc., and made part of The Duriron Company’s standard product. Duriron spray nozzles are sometimes used to replace the Duriron exhaust fan, and in small installations i t has been found that these spray nozzles perform the dual service of furnishing the necessary draft, a t the same time condensing the gases so that they may be discharged t o a sewer. Although The Duriron Company holds the patent rights to such type apparatus, they have, of course, no objection t o
EVALD dXDERSOS
WESTERS PRECIPITATION COMPANY Los ANGISLRS. CALIF. April 4 , 1927
Calendar of Meetings American Chemical Society-74th Lleeting, Detroit, l l i c h , , September 5 to 10, 1927. Division of Colloid Chemistry-Fifth Sational Colloid Symposium, University of Michigan, Ann .4rbor, >rich., June 22 to 24, 1927. Institute of Chemistry-State College, Pa., July 4 to .XI, 1927. Division of Organic Chemistry-Second Na tiona! Symposium on Organic Chemistry, Columbus, Ohio, December ’“3 to 31, 1927. First International Congress of Soil Science-LT-ashington, D. C., June 13 to 22, 1927. American Leather Chemists’ Association-Cincinnati, Ohio, June 15 to l i , 1927. American Society for Testing Materials-Annual lfeeting, French Lick, Ind., June 20 t o 24, 1927. American Electrochemical Society-Fall llleeting in the form of a n excursion through the Northwest, September 4 to 20, 1927. 1l t h Annual Exposition of Chemical Industries-Grand Central Palace, l;ew York, h’.Y . , September 26 to October 1, 1997.
