INDUSTRIAL AND ENGINEERING CHEMISTRY
276
READINGS OF MANGANESE AND COPPER LINES TABLE I. DENSITOMETER Mn Plate 1 Conon. M n Cu
Plate 2 hln Cu
Plate 3 hXn Cu
46.7 41.8 30.3 23.6 15.9 6.7
42.2 37.0 28.1 19.8 12.6 6.2
Plate 4 Iln Cu
Plate 5 hln Cu
Plate 6 Mn Cu
Mg./cc. 0.5 0.25 0.10 0.05 0.025 0.01
46.9 39.6 30.4 23.1 15.5 8.1
23.6 22.0 23.6 24.9 23.6 24.0
23.1 24.1 23.7 23.0 23.2 23.2
21.1 42.2 2 0 . 0 42.0 2 0 . 8 2 1 . 2 3 6 . 2 2 0 . 0 3 6 . 1 21.1 22.1 26.5 20.3 27.5 21.3 20.3 19.3 21.2 18.6 20.4 21.0 13.1 21.2 13.7 21.8 21.6 6.522.5 6.521.5
LINETO TABLE 11. RATIOOF DENSITIESOF MANGANESE COPPERLINE
A?.
Mean DeviaPlate Plate Plate Plate Plate Plate Aver- Devia- tion of Concn. 1 2 3 4 5 6 age tion Mean
Mn
Mg./cc. 1.99 2.02 2.00 2 . 1 1 2.02 2.08 2 . 0 3 0.036 0.014 0.5 0.25 1.80 1.73 0.10 1.29 1 . 2 8 0.05 0.93 1.02 0 . 0 2 5 0.66 0 . 6 8 0.01 0.34 0.29
1.74 1.81 1.27 1.31 0.98 0.91 0.60 0.62 0.29 0.29
1.71 1.29 0.91 0.63 0.30
1.74 1.42 0.96 0.68 0.34
1.75 1.31 0.96 0.64 0.31
0.031 0.036 0.035 0.030 0.021
0.012 0.014 0.014 0.012 0 0086
17.1 21.7 20.0 22.9 22.8 24.0
35.7 37.7 28.5 22.1 15.6 8.1
VOL. 12, NO. 5
The lines chosen were free of any background, The ratio of the density of the manganese line to the copper line was plotted against log concentraso that no correction was necessarv. c:nm Y’”lL*
Table I gives densitomete: readings of the manganese line at 2576’12 and the copper line a t 2369.8 =1. for different manganese concentrations. Six separate plates were exposed, using the same standard manganese solutions. Table I1 gives the ratio of the densities of the manganese line to the copper line, the average ratio value, mean deviation, and average deviation of the mean. When the average ratio values are plotted against the log-concentration (mg. of manganese per cc.), a curve is obtained, as shown in Figure 2.
Literature Cited
The electrodes were placed a t a distance of 60 cm. from the slit of the spectrograph. The spark gap was adjusted to 6 mm., and duplication of the gap distance was accomplished by the use of a glass spacer 6 mm. thick. No external condensing lens was used. A Bausch & Lomb large Littrow (quartz) spectrograph was employed, using a slit width of 70 microns and 4-mm. height. Prism position 7, covering the range 2300 t o 2900 A., was used to register the section of spectrum which contained the manganese and the copper lines selected.
(1) Gerlaoh, W., and Schweitzer, F., 2.anorg. allgem. Chem., 195, 255 (1931). (2) Jolibois, P., and Bossuet, R., Compt. rend., 204, 1189 (1937). (3) Lowe, Fritz, “Optisohe Messungen des Chemikers und Mediziners”, 2nd ed., pp. 53-7, Dresden and Leipzig, Verlag von Theodor Steinkopff, 1933. (4) Lundegardh, H., “Quantitative Speotralanalyse der Elemente”, p. 96, Jena, Verlag von Gustav Fischer, 1929. (5) Twyman and Hitchens, Proc. Roy. Soc., -4133,72-92 (1931).
Dry Ice as a Preventive of Atmospheric Oxidation GEORGE E. FERGUSON AND LEOPOLD SCHEFLAN Pyrene Manufacturing Company, Newark, N. J.
I
T IS well known that tin in commercial tin-lead solders
can be determined accurately by titration with standard iodine solution, provided that it is present entirely as stannous ion in hydrochloric acid solution (1). The use of solid carbon dioxide has been found helpful in preventing oxidation of the stannous ion previous to the titration.
I
2.0
2.2
1.4
P.6
%2
70
i2
I i.4
i.6
LOG CONCENTRATiON
FIGURE 2
Excitation of the sample was obtained by a high-potential spark supplied from a 220-volt source, with sufficient resistance to produce a current of 17.5 amperes in the primary of a 1000 to 1 5-kw. transformer. The secondary circuit consisted of 8 condensers (in parallel) of 815 X microfarad each. No inductance coil was used in the secondary circuit. The solutions were analyzed by the technique already described, and the spectra were recorded on Eastman D. C. (double-coated) orthochromatic plates. The plates were processed using Eastman standard x-ray developer and fixer, and were developed for 5 minutes a t 18” C. After development, they were fixed for about 20 minutes, washed in running water for a t least one hour, rinsed in distilled water, and dried in air. The Gaertner visual microdensitometer, having a scale range of 0 to 100 divisions corresponding to density units of 0 to 4, was used to evaluate line densities.
After a sample of solder filings has been prepared and dissolved in hydrochloric acid in the usual way, and any tin in the stannic form has been entirely reduced to the stannous form, immediately place a small piece of solid carbon dioxide in the solution and place the flask in a cooling bath of ice and water. Add more small pieces of dry ice and maintain a vigorous evolution of gaseous carbon dioxide within the Erlenmeyer flask until the solution has been cooled t o room temperature and is ready for titration. Just preceding the titration, wash down the wall of the Erlenmeyer flask with distilled water containing a small piece of dry ice, add 5 ml. of starch solution as indicator, and titrate the solution with 0.10 N iodine solution. The use of solid carbon dioxide prevents the formation of stannic ion due to atmospheric oxygen, makes it unnecessary to employ a bicarbonate of soda solution as a wash water, and eliminates the necessity of setting up apparatus for passing gaseous carbon dioxide or any ot,her gas through the solution during cooling. Dry ice may serve equally effectively in other determinations where protection of the solution from atmospheric oxidation is important.
Literature Cited (1) Scott, W. W. “Standard Methods of Chemical Analysis”, pp. 426-8, New York, D. Van Yostrand Co., 1917.
