Modified Hydrogen Evolution Method for Metallic Magnesium, Aluminum, and Zinc RAYMOND H. KRAY,Naval Powder Factory, Indian Head, Md.
C
HEMICALLY this method
THERMOMETER type pinchcock,which can be operated with one hand, is the best to use, C8PILLrWY GL6SS is the same as the Meyer !caving the other hand free for ourTUBING hydrogen evolution method ing. After clamping the pinclcock (2), depending on the measurement SPLIT CORK MADE and making sure the rubber tubing of hydrogen gas evolved by metals is completely filled with water, the TIGHT WITH SEFILING WflX reaction bulb is connected to the acting on dilute sulfuric acid. The eudiometer as shown. About 1 inch apparatus and technic used, how(2.5 cm.) of distilled water is poured ever, offer a quicker, m o r e coninto beaker D around the reaction venient, and more accurate way of tube, and the pinchcock is removed. The reaction can now be started determining m e t a l l i c magnesium, A little concentrated sulfuric acid is aluminum, and zinc than is obtained poured into beaker D,the stopcock on WATkR by the Meyer method. AGlTIlTOR the eudiometer opened, and leveling The glass i m m e r s i o n filter (S), bulb C slightly lowered, so as to draw a little acid into the immersion filter. which is the essential feature of this At first, caution should be used so method, affords a m e a n s of conthat the flow of gas is slow, until a trolling the speed of r e a c t i o n by gap is formed between the levels of allowing acid to be drawn into or liquid in B and A . Action is then increased by lowering C as required. driven out of the reaction tube a t About two or three times during a will by the simple e x p e d i e n t of determination leveling bulb C is lowering or raising the leveling raised, and the liquid in A partially bulb. In the same way any acexpelled. On lowering C again, fresh IY acid is drawn in and the reaction cumulation of salts formed by the continues with renewed vigor. On r e a c t i o n c a n b e flushed out a t completion of reaction, levelingbulb C regular intervals without danger of is slowly lowered and all remaining gas losing gas, keeping the surface of in A and in the tubing is drawn into the eudiometer and after standing 5 FIGURE1. DIAGRAM OF APPARATUS the metal constantly exposed to minutes is measured in the usual way. fresh acid. W h e n the evolution of gas is completed, it can easily be drawn into the eudiometer Barometer and temperature readings are closely checked without any difficulty from trapped gas bubbles, which one and calculation made according to the formula frequently encounters in the regular method. The immersion filter used was made of Jena glass, with a 1 - (0.00018 x t ) = (P’- u)V’ fused-in sintered filter disk 3 mm. thick. These tubes are T T’ 1 made in three degrees of porosity-coarse, medium, and fine. x 100 = per cent free metal in sample The tube used was of medium porosity, and was of 30 cc. capacity. The other parts of the assembled apparatus are X = volume of hydrogen, under standard conditions of temillustrated in Figure 1. perature and pressure, generated by same weight of metal of 100 per cent purity The eudiometer tube was especially designed for this method. As illustrated it has a capillary tube on top for This method has been used successfully with magnesium entrance of gas, and is graduated in 0.1 cc. between the 320samples of various degrees of purity and fineness, and has been cc. and 400-cc. mark. found applicable for all grades up to and including 150-mesh material. PROCEDURE
9
c v
xv
The apparatus is assembled preferably in a room with fairly even temperature and no drafts. All rubber connections are made secure with wire, and eudiometer tube B is filled com letely with distilled water, saturated with hydrogen. The metafequivalent to about 360 cc. of hydrogen gas at standard conditions of temperature and pressure, is wei hed into the dry immersion ater, A . (The eudiometer was cali%ratedfrom 320 to 400 cc.) A piece of thick-walled rubber tubing, of 0.188 inch (0.47 om.) inner diameter and 4 inches (10 cm.) in length, is next connected with the filter. Distilled water saturated with hydrogen is poured rapidly into the filter until it flows over the top of the tubing, at which time a pinchcock is clamped on the rubber tubing, stopping the flow of water through the porous filter and preventing air from entering the tube from the top. While filling, the slow downward flow of water through the gorow disk keeps the finer mesh metals in the bottom of the tube. y using hydrogen-saturated water, preferably at 15” to. 20’ C., in filing the tube little difficulty is experienced even with very fine magnesium powder of a high degree of purity. A spring250
OF LABORATORY TESTS TABLEI. RESULTS
METAL Magnesium ribbon Magnesium 35-80 mesh Magnesium 100-mesh Magnesium 100-mesh Sample 120 Magnesium 150-mesh. Sample A Magnesium powder. Sample D. 100-mesh Magnesium powder 5 Aluminum wire
MODIFIED COPPBR ALUMINUM GAS EVOLUTION OXIDE C H L O R I D ~ METHOD METHOD(^) METHOD(^) ... 99.89 &:a7 99.88 9S.30 98.11 98.28 98.11 98.41 98.16 98.15 97.47 9i:il 97.64 97.68 ... 97.35 98.99 ... 99:os 99.21 99.20 99.09 ... 92: 40 92.41 ... 92.33 ... 97:s1 97.42 97.71 ..* 97.67 97.50 97.88 95.13 95.18 .** 94.85 99: 81 99.70 99.73
*.. ... ... .... .. ....* .
...
.... ..
... ...
... ...
... ... ...
July 15, 1934
INDUSTRIAL AND ENGINEERING CHEMISTRY
Zinc and aluminum (but not aluminum powder) can also be determined in this way* In the case of aluminum, a sodium hydroxide solution is used as a reagent. Some results obtained a t this laboratory by different analysts over a period of about 4 years are given in Table I. The- time required for an analysis of magnesium varied from 2 to 4 hours, depending on the temperature of the room. No heat was applied to speed up the reaction, but be used to advantage when the loom perature is very low or when less reactive metals than magnesium are being analyzed.
251
ACKNOWLEDGMENT The author wishes to thank J, A, O’Callaghan, T. C. Jenkin, and F. Thames of this laboratory for analytical work done in connection with this method. LITERATURE CITED (1) Bluminum Co. of America, Methods. (2) Scott, “Standard Method of Chemical Analysis,” pp. 487-8, D. Van Nostrand Co., N. Y., 1920. (3) Thomas Co., Arthur H., “Laboratory Apparatus and Reagents,” p. 367. R E C ~ I V EMaroh D 5, 1934.
Furoic Acid as an Acidimetric Standard HENRYB. KELLOGAND ADA M. KELLOG,The AMP Research Laboratories, Corona, L. I., N. Y.
T
HE suitability of furoic acid as a primary standard was suggested by experience gained in purifying the acid for use of its derivatives as bactericides. In these experiments it was necessary to prepare by sublimation from the technical grade an acid of the highest purity. The acid was then titrated with an alkali previously standardized by the Bureau of Standards-Standard Samples No. 39d, benzoic acid, and No. 84, acid potassium phthalate. It was observed that the purified furoic acid could be titrated with the standardized alkali to a high degree of accuracy and that this titration afforded the most rapid and accurate method of determining the purity of the sample of furoic acid, which finally led to the determination of its applicability as a 6tandard The method used in studying the applicability of furoic acid was indirect, standardizing the standard alkali by Bureau of Standards samples. Upon analysis the furoic acid showed the following results :
.
Melting point Moisture Nonvolatile matter Acidity (as furoio acid with phenolphthalein)
128-9’ C. 0.25% 0.02yo 99.72%
This sample was purified by crystallization from water. After drying, the melting point was found to be 129.6’ C. After subliming the melting point became 131’ C.; resubliming gave no change in the melting point, which remained constant at 131’ C. A sample of this purified furoic acid exposed to the regular laboratory conditions for 3 months showed a gain of 0.04 per cent moisture, indicating that it was slightly hygroscopic, but this slight trace of water was readily removed by careful fusion. The sodium hydroxide solution used was prepared free from carbonates. It was carefully protected from the carbon dioxide of the air by guard tubes and all titrations were performed on the same day in order to avoid possible errors in the titrations due to contamination by carbonates. The apparatus in which the titrations were performed was that of Jackson.’
solution of phenolphthalein were added, and the solution was titrated with the approximately 0.1 N alkali. The results obtained are shown in Table I. TABLEI. BENZOIC ACID (99.98per cent pure Bureau of Standards Sample No. 39d) WEIQHTOF NaOH RELATIVE CORRECTXID No. SAMPLE USED NORMALITY NORMALITY Gram cc 1 0.3241 25.49 0.10417 0.10415 2 0.3419 26.90 0.10414 0.10411 3 0.2551 20.07 0.10414 0.10411 4 0.3133 24.64 0.10418 0.10415 5 0.2981 23.44 0.10420 0.10417 6 0.3091 24.32 0.10413 0.10410 7 0.2446 19.24 0.10416 0.10413 Mean of seven determinations 0.10413
.
STANDARDIZATION BY POTASSIUM PHTHALATE The second step was to repeat the standardization by the use of potassium acid phthalate. These titrations were performed as described in Certificate No. 84, U. 8. Bureau of Standards, and the results obtained are recorded in Table 11. TABLE11. POTABSIUM ACID PHTHALATE No. 1 2 3 4 5 6
(99.97per cent pure Bureau of Standards Sample No. 84) NaOH WEIGHTOF R ~ L A T I V E CORRECTED SAMPLE US~D NORMALITY NORMALITY Gram cc. 9.98 0.10416 0.10411 0.2122 0.10421 0.10417 0.2319 10.90 0.3115 14.64 0.10422 0.10418 0.2535 11.92 0.10417 0.10413 0.2242 10.54 0.10419 0.10416 0.3575 16.80 0.10423 0.10419 Mean of aix determinations 0,10415
STANDARDIZATION OF FUROIC ACID Before using, the purified furoic acid was fused in a covered platinum dish over an air bath. The temperature during the fusion did not exceed 142’ C. Upon completion of the fusion the acid was cooled in a desiccator. Various weighings were transferred into the titrating apparatus, 25 to 50 cc. of previously boiled distilled water were added, and the apparatus was swept free from carbon dioxide. The sample was allowed to stand until the acid had dissolved and then titrated. The results are shown in Table 111. STANDARDIZATION OF SODIUM HYDROXIDE BY BENZOIC ACID TABLE111. FUROICACID The first step was to standardize the sodium hydroxide WEIGHTOF NaOH No. SAMPLE USmD NORMALITY solution by the use of benzoic acid which was fused and cooled Uram cc before using. The titration was performed according to the 25.08 0.10417 1 0.2927 0.10411 2 0.2033 17.43 directions in Certificate No. 39d for benzoic acid, U. S. Bureau 40.73 0.10418 3 0.4754 of Standards, using the Jackson titrating apparatus. Various 25.72 0.10411 4 0.3000 28.45 0.10419 6 0.3321 weighings of benzoic acid were taken, 3 drops of a 1 per cent 6 n .2x62 24.52 0.10418
.
1 Jackson, J., J .
SOC.Chen. Ind.,63,36 (1934).
Mean of six determinations 0.10415
