ANALYTICAL EDITION
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Vol. 5 , No. 5
ether is separated from the water and run into a 100-ml. glass- for 16 hours. The ether was then transferred to a distillation stoppered graduate. It is best to shake out the water in the flask and 2 ml. of alcohol and a known weight of o-nitrotoluene separatory funnel with another portion of pure ether. added. The process was then carried out exactly as has been DETERMINATION OF 0-NITROTOLUENE BY REFRACTOMETER. described. The ether containing the o-nitrotoluene is cooled to 25" C. RESULTB SHOWING ACCURACY OF METHOD in a constant temperature bath, and the volume noted. After WEIGHT OF WEIGHT OF determining and checking the refractive index, the percentage 0-NITROTOLUENE 0-NITROTOLUENE ADDED FOUND ERROR by volume of o-nitrotoluene in the ether solution is read Grams Urams % from curve shown in Figure 1. 1.0286 1.0070 '-2.1 The volume of the ether solution of o-nitrotoluene, multi0.8470 0.8344 -1.5 0,8800 0.8661 -1.6 plied by the percentage by volume of o-nitrotoluene, multiplied by 1.168 (specific gravity of o-nitrotoluene), equals the TESTSON ACTUALPOWDER weight of o-nitrotoluene in ether extract from powder. SAMPLE OB POWDER PREPARATION OF CURVE. The curve shown in Figure 1 DETERMINATSONS No. 1 No. 2 No. 3 is made by testing known weights of o-nitrotoluene, specific Final volume of ether solution at 25' C. 44.0 46.0 45.5 and Lomb immersion refractometer gravity 1.168, dissolved in 25 ml. of pure ether, washed with Bausch reading a t 25' C., prism A (scale divisions 0 t o 100, prism A,hover a range of index water, with the immersion refractometer, prism A a t 25" C. 1.3254 t o 1.3664). 69.5 69.2 68.3 The volume of the o-nitrotoluene is calculated in milliliters Pervalues cent o-nitrotoluene corresponding t o above refractometer readings 1.72 1.67 1.68 from the weights and specific gravity and plotted on the Volume o-nitrotoluene in cubic centimeters 0.7568 0.7682 0.7644 curve against the refractometer readings as per cent by volume Weight o-nitrotoluene in grams 0.8839 0.8918 0.8928 o-nitrotoluene in powder not correctof ether solution, It would be more convenient for calcula- Peringcent for volatiles 4.42 4.46 4.46 o-nitrotoluene in powder correcting tion to have a definite volume of ether solution, and have the Perforcent volatiles and moisture 4.58 4.62 4.62 graph give directly the weight of nitrotoluene in the sample. Twenty grams of powder were taken for each test. Total volatiles = The authors found it simpler and perhaps more accurate, 8.07 per cent. powder, when manufactured, was calculated t o contain about 4.50 however, not to adjust the volume of the ether solution ob- perThe cent o-nitrotoluene. tained a t the end of the process. If the other method is preferred, the amount of ether solution can be set a t a definite ACKNOWLEDGMENT figure, say 50 ml., and the graph so adjusted that it will give The authors wish to express their appreciation to Walter W. directly the weight of nitrotoluene corresponding with any Farnum, chief chemist, Kava1 Powder Factory, for helpful refractive index for this volume. suggestions, particularly that the refractometer be used for EFFECT OF ALCOHOL UPON REFRACTOMETER READINGS this method. Even as small an amount as 1 per cent of alcohol by volume in the ether changes the refractive index sufficiently to vitiate results. It is therefore necessary that all the alcohol be completely removed from the nitrotoluene. ACCURACY OF METHOD Standards were run as follows: 20 grams of nitrocellulose were placed in the Wiley extractor and extracted with ether
LITERATURE CITED (1) Callan and Henderson, J. Soq, Chem. Ind.,41, 157T (1922). (2) Knecht, E.,and Hibbert, E., New Reduction Methods in Volumetric Analysis with Additions," Longmans, 1918. (3) Storm, C. G., Orzg. Com. 8th Intern. Congr. A p p l . Chem., 4, 117 (1912). RECEIVED January 27, 1933. Published with permission of the Bureau of Ordnance, Navy Department.
Determination of Zirconium in Plain Carbon and Alloy Steels THOS.R. CUNNINGHAM AND R. J. PRICE Union Carbide and Carbon Research Laboratories, Inc., Long Island City, N. Y.
I
N A PREVIOUS article (1) a method for the determination of zirconium, based on the rapid precipitation of Zr(HPO& in the presence of varying amounts of a number of other elements, has been described. Inasmuch as several workers have experienced some difficulty with the procedure as outlined, and since complete precipitation of the zirconium in the presence of ferric chloride depends upon a rather close control of the acidity of the solution, the following details concerning the decomposition of the sample and the initial separation of zirconium are offered.
PROCEDURE Five or 10 grams (depending upon the amount of zirconium present) of the drillings are transferred to a 600-cc. covered beaker and treated with hydrochloric acid (sp. gr. 1.19), 40 cc. being used for the 5-gram and 60 cc. for the 10-gram sample. The contents of the beaker is heated to 80" to 90" C. until all action appears to have ceased, when from 8 to
15 cc. of Perhydrol (30 per cent hydrogen peroxide) diluted with 25 cc. of water are introduced. The solution is heated for 1 or 2 minutes longer and diluted with warm water to 350 cc. Ammonium hydroxide (1 to 1) is added slowly until a permanent precipitate forms, followed by hydrochloric acid (1 t o 1) dropwise, with stirring, until the precipitate just disappears. From 10 to 20 grams (a sufficient amount to reduce the iron to the ferrous state) of sodium sulfite dissolved in 50 cc. of hot water, and 20 cc. of hydrochloric acid (sp. gr. 1.19) are added in the order named and the contents of the beaker is stirred for 1 minute. Eight grams of diammonium phosphate dissolved in 50 cc. of water are added to the solution of 5 grams of steel or 10 grams to the 10-gram sample. The solution is stirred vigorously for several minutes and the determination completed as described ( 1 ) . The final ZrPzOr precipitate is tested for titanium as follows: The ignited and weighed precipitate is fused with several grams (a sufficient amount) of sodium carbonate, the melt leached with
September15,1933
INDUSTRIAL AND ENGINEERING CHEMISTRY
hot water, and the solution cooled t o room temperature. The solution is filtered on a 9-cm. paper containing some ashless paper pulp and the paper and residue are washed 18 or 20 times with 2 per cent ammonium nitrate solution to remove sodium salts. The paper and precipitate are ignited in a platinum crucible at a dull red heat until the carbon of the filter paper has been completely burned, fused with 1 or 2 grams of potassium pyrosulfate, and the titanium is determined colorimetrically. The weight of titanium found, multiplied by 3.16, gives the weight of TizPzOsto be deducted from the combined weight of zirconium and titanium phosphates. The weight of ZrPz07found, multiplied by 34.39 and divided by the weight of sample taken, gives the percentage of zirconium. Should the amount of titanium found account for the greater part of the combined weight of zirconium and titanium phosphates, then it is suggested that more 30 per cent hydrogen peroxide be added than that used for the colorimetric determination and the zirconium precipitated by the addition of 3 grams of diammonium phosphate, digestion, filtration, and ignition as described in the previously cited article.
It is well known that Zr(HPOJ2 is completely precipitated from relatively strong hydrochloric acid solution in which the iron is present in the ferrous condition. Hence, in dealing with plain carbon and manganese steels the treatment with hydrogen peroxide may be omitted. However, in working
335
alloy steels, especially those containing strong carbide-forming elements, the addition of hydrogen peroxide is necessary for the decomposition of the material. The results obtained by the procedure described are shown in Table I. TABLEI. DETERMINATION OF ZIRCONIUMIN STEEL STEEL ZIRCONIUM ZIRCONIUM T A K E N ADDED FOUND ERROR Grams Gram Grana Grana 1 Plain C 10 0.00047 0.00045 -0.00002 2 PlainC 10 0.00094 0.00093 --0.00001 3 Plain C 5 0.0045 0.00455 $-0.00005 4 CrWVa 5 0.00235 0.00284 --0.00001 5 CrWV 10b 0.00094 0.0009 --0.00004 0 Bureau of Standards standard sample 50 A. b Two 5-gram portions were taken and the precipitates combined after making the sodium carbonate fusion t o separate the tungsten.
EXPERI- KINDOF MENT STEEL
LITERATURE CITED (1) Cunningham, T. R., and Price, R. J., IND.ENQ. C~nnf.,Anal. Ed., 3, 105 (1931). RECEIVED June 1, 1933.
Microburet for Potentiometric Microanalysis H. L. LOCHTEAND ANNA HOOVER, Department of Chemistry, University of Texas, Austin, Texas
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ESULTS obtained by the junior author show that then assembled as shown and with the stopcock open and the micropotentiometric titrations using 1 cc. or less of buret filled with water the braking capillary is shortened by solutions with a normality of 0.1 to 0.01 are feasible and yield breaking off small pieces until drops are delivered st the rate an accuracy in favorable cases of 0.1 to 0.2 per cent, provided of 60 to 120 per minute. The next adjustment is that of the capacity of the tube the volume increments near the equivalence point are sufficiently small and uniform. The remarkable results just above the stopcock. If this is too large, a single turn of the reported by Schwarz (3) more than confirm the authors' stopcock results in delivery of several drops; if it is too conclusions in regard to the applicability of potentiometric small, a turn does not always yield a drop. The capacity titration methods to small volumes. Their early results is adjusted by changing the length of glass rod inserted above led to the development of a buret that delivers dependably the stopcock until single drops are obtained on turning the single uniform drops with a volume of about 0.01 cc. Since cock once. In use the pipet is filled by removing the braking capillary graphical or, preferably, Hahn's methods (1) permit estimaand filling by suction through a piece of rubber tion of the end point to one-tenth of this increment, tubing. In titrations the solution-may be added it is evident that the accuracy obtainable in suitable titrations is satisfactory for any ordinary micro rapidly until within 0.1 to 0.1.5 cc. of the end point. A few drops a t a time are now added until the uses. potential shows that the end point is approaching. Figure 1shows the buret finally adopted. For conThe exact volume used thus far is now read with venience in cleaning and in building and adjusting the the aid of a lens and further additions are made various parts, these were merely connected by highin single drops until 3 or 4 drops past the end point. grade clean rubber tubing a t the places shown. A Since several minutes are usually required1 to obtain ground-glass joint could be substituted for the uppera stable potential, the exact volume may be read most connection and the others could be eliminated again in the immediate neighborhood of the end point. by fusing the parts together, but this would involve The exact end point is then determined by one of the considerable cost and inconvenience and would yield methods mentioned and the volume read to 0.1 drop. no increase in accuracy. The graduated section is The drop volume should be redetermined daily by obtained from a high-grade pipet graduated to 0.01 counting the number of drops of the solution decc. and delivering 1 cc. The dimensions shown were livered between the 0.5- and 1.0-cc. marks. Since found satisfactory and, in case of the tip, essential. the drop volume depends partly on the hlydrostatic The tip with the length shown has a capillary with head, very accurate work requires determination, an outer diameter of about 0.5 mm. It is paraffined once for all, gravimetrically of the relation between by passing a continuous stream of low-pressure air drop volume and buret reading, but this precaution through it while dipping momentarily into melted is hardly necessary in ordinary work. The time reparaffin and then cooling till this solidifies. A tip quired for a complete titration with this buret is not that ceases to give small drops may often be repaired greater than that used with macroburets. by connecting to the air supply and remelting the paraffin by holding it above a flame. LITERATURE CITED The braking capillary a t the top is similar to that (1) Hahn, Z.anal. Chem., 87,263 (1931). of Ormond (2) but made from ordinary glass tubing (2) Ormond, Ibid., 75, 209 (1928). I6'MM. that is permitted to thicken in the flame and is then (3) Schwarz, K., Mikrochem., 13, 6 (1933). drawn out to a very fine capillary. The parts are FIGURE 1 RECEIVED May 23, 1933.
