V O L U M E 21, NO. 5, M A Y 1 9 4 9 Housing. Rooms will be available in the university. dorinitories for Thursday, Friday, and Saturday nights, June 23 to 25. Accommodations for married couples and single women can be provided, although these may be somewhat limited. There are only a few single rooms available and double occupancy is urged. Rates for individuals are $3.50 (including 50-cent deposit for the key) for the whole period of stay-one, two, or three nights. Married couples will be charged $5.50 (including 50-cent deposit for key). Bedding will be provided but the university cannot supply tonels. .lrrangements can be made for some rooms in private homes adjacent to the campus a t prices ranging from $3 to $5 per night. Special mention should be made on t,he application form if such accommodations are desired. Meals. Meals will be served through special catering. It is therefoi,~rspecially necessary that rccwation? be sent in before
SIR: In a recent paper in this journal Aid:inia[ A i ~ CHEX., -~i~ 20, .. 891 (19iS)l claimed that the polarographic half-wave potential for the reduction of Ti (IS:) to Ti (111) in a supporting electrolyte composed of 1 X sulfuric acid, 8% urea, and saturated with SOdium oxalate is greatly dependent on the concentration of titanium. He reported a negative shift of over 0.4 volt when the concentration of titanium was increased from 0.06 to 9.3 millimolar.. Adams also claimed that the half-wave potential of tithnium in the foregoing supporting electrolyte undergoes a large negative shift, (ahout 0.5 volt) when ferric iron is added in concentrations up to 19 millimolar. According to our experience these conclusions are erroneous. R e have repeated Adaina' measurements with identically t,he same supporting electrolyte ( I ATsulfuric acid, S70 urea, saturated with sodium oxalate). The measurements were made a t 25' C. with a low-resistance H-cell [Lingane and Laitinen, ISD. ENO. CHEW,ANAL.ED.,11, 504 (1939)] containing a saturated calomel anode. The cell resistance was less than 500 ohms, and hence correction for iR drop was negligible. Polarograins were recorded with a calibrated Sargent-Heyrovsk4 ;\Iode1 X I photographic polarograph, whose reliability has been conclusively established. Air was removed from the solution with pure nitrogen. With concent,rations of titanium between 0.46 and 14 millimolar we found that the half-wave potential was constant, a t -0.285 * 0.005 volt versus the saturated calomel electrode. Furthermore, we found that ferric iron in concentrations up to 15 millimolar does not, have any appreciahle influence on the half-wave potential of titanium. We believe that Bdams' erroneous conclusions are due primarily to his use of a cell with a very large resistance, and his failure to correct for the correspondingly large iR drop. This correction is a linear function of the current a t the half-wave point, and hence of the concentration of reducible ion. Adams does not describe his cell in detail but does mention the use of a Beckman No. 9740 saturated calomel reference electrode, which is known to have a large resistance. This type of electrode is intended only for potentiometric (null point) measurements, and is entirely unsuitable as a working reference anode for polarographic measurements. I t is also known that the type of recording polarograph used by Adams yields erroneously large values of half-wave potentials as a result of recorder lag, and this error increases witjh increasing wave height. SS'e have not been able to confirm Xdams' conclusioii that urea has a beneficial influence on the wave form of titanium, and have found that it does not function satisfactorily a,s a maximum sup-
649 the meeting. The priw for lunch on Friday, the banquet Friday evening, and breakfast and lunch on Saturday will be $8.50. Arrangements can be made separately for the banquet alone at a price of $3.50. Transportation. Middletown may be reached by the New York, Seiv Haven, and Hartford Railroad (Springfield line) to hkriden, Conn. These trains run on daylight saving time from Grand Central Station. Bus service to Middletorvn connects with all trains a t the Meriden station. Those coming from the west via Neiv York Central may prefer to come down from Springfield, PIIa\s., to Meriden. If there is sufficient indication ahead of time as to the numbers arriving by various trains, special arrangements m-ill be made for transportation from Meriden. Ask the bus driver to let you off a t Downey House, which ir: o n the I17cslej-ancampus in Middlctown.
SIR: The procedure outlirieti in this journal [ h s a ~CHESI., . 20, 891 (19iS)l for the polarographic determination of titanium has been used with success for control work during t,he pilot plant operation of the extraction of alumina from clay. .idditional detwminat,ions of titaniuni in alumina which had been treated with hydrogen fluoride and aluminum fluoride have been completed by this procedure, as t,heusual colorimetric procedure for titanium using hydrogen peroxide was not applictnhle in the preseirce of fluoride owing to the bleaching effect. The conditions for the analysis were outliiird in the paper --i.e., a high resistance calomel electrode and a Leeds & Sorthrup Electrochemograph. No correction was made for the iR drop. I am not familiar with the characteristics of the Sargeiit-Heyrovsk4 type polarographs, and am thus unable to compare the conflicting conclusions. The effrct of urea, as well as a large number of comnionly einployed maximum suppressors, was thoroughly studied, and it w m found that the specified concentration of urea was both adr,quate and necessary under the conditions st,:tted in the procedure. DOSALD F. .\DAMS State College of Washingtoil Pullnian, Wash.
Armour Research Foundation, Stevens Hotel, Chicago, Ill., June 0 to 11 American Council of Commercial Laboratories.' Curtis Hotel, Minneapolis, Minn., June 23 and 24 Symposium on Fine Particles and Resolution.
American Society for X-Ray and Electron Diffraction. Corne11 University, Ithaca, N. y., June 23 to 25 Second Annual Summer Symposium on Analytical Chemistry. Wesleyan University, Middletown, Conn., June 24 and 25 Fourth Instrument Conference and Exhibit. Municipal Auditorium, St. Louis. Mo., September 12 t o 16
