ANALYTICAL
EDITION
Industrial Chemistry
VOLUME6 NUMBER 3
MAY15,
AND ENGINEERING
1934
P U B L I S H E DB Y T H E A M E R I C A NCHEMICAL SOCIETY HARRISON E. HOWE,EDITOR
Quantitative Spectroscopic Analysis of Solutions WALLACE R. BRODEAND JAMESG. STEED,Department of Chemistry, The Ohio State University, Columbus, Ohio
T
Calibration curves have been determined for the Figure 143). A logarithmic secquantitative spec~rographicanalysis of columtor (2, 3) was used in front of logarithmic sector method (1-4) data have been obthe slits of each of these intrubium, titanium’ vanadium~lungsten’ ments, actuated by connection tained on the quantitative estiiron, chromium, lead, and with the starter knob of a simmation of columbium, beryllium, titanium, vanadium, tungsten, These curves are given in both per cent of eleple alternating current electric ment and logarithm of the per cent of element clock. I n a modification of the iron, molybdenum, chromium, lead, and cobalt. Data on a few present. T ] average ~ ~ deviation in the ,jeterTwyman and Hitchen solution of these elements (chromium, spark apparatus 22-gage copper mination of samples of known composition was lead, and cobalt in particular, electrodes were used for both 6) have heen prepared by other less than 5 per cent of the known concentration. the upper and lower electrodes workers, but using different line in place of the previously recpairs from those in the present analyses. ommended carbon and gold electrodes. A Pyrex jet was The method of analysis follows in general that described found to be as satisfactory as a quartz jet. The copper by Twyman and Hitchen (6) with certain modifications in lines produced in the spectra (Figure 1)were not objectionable the apparatus and manipulation. Two different quartz and may reduce to some extent the slight error due to an exspectrographs were used in this study, a large Hilgero(E-185) cess of a foreign anion in the solution to be tested. The spark was produced by a 20,000-volt 2-kilovolt-amLittrow spectrograph (linear dispersion 7000 to 2000 A. = 100 cm., Figure 1-A) and a medium Bausch and Lomb Spectro- pere transformer. The primary (110 volt) circuit had a graph, No. 2820 (linear dispersion 7000 to 2000 8. = 21 cm., resistance in it, to permit the passage of about 1 ampere. HR”0UGH the use of the
TABLEI. QUANTITATIVE SPECTROGRAPHIC ANALYSISOF SOLUTIONS
COMPOUND USED
METHOD OF SOLUTION
Columbic anhydride
KaCO3 fusion plus water
Beryllium sulfate
Water plus 2% HzSO4
Beryllium sulfate
INTERNAL CONCBNTRATION STANDARD CONCENTRATION OF RANQE(ELEMENT)USED STANDARD % Qrams/100 cc. water 0.005 to 1 . 0 KMnO4 2.8769 (1% Mn) 0.0001 t o 0 . 1 Bi(N0s)a. 5Hz0
AMOUNT OF STANDARD ADDEDTO 100 cc. OF
SOLUTION Cc. 20 Cb Mn 50
8.6580 grams BiOzCOa. 1/z Hz0 dissolved in excess conc. HNOa and di,luted to 100 cc. (3.5%
B1)
Bi
Water plus 2% HzSO4
0.0005 to 1 . 0 KMn04
Titanium dioxide
Sop3imdjgmulfate fusion plus
0.005 to 1 . 0
CrOs
10.0000 ( 5 . 2 % Cr)
16.7
Vanadic anhydride
HCl (calculated amount plus 2%) 0.005 to 1 . 0
CrOa
19.2308 (10% Cr)
20
Tungstic anhydride
NaOH (calculated amount plus 2%) Water plus 2% HzSO4
Ferrous ammonium sulfate Molybdic anhydride
”,OH 2%)
(calculated amount plus
2.8769 (1% Mn)
10
0 . 0 0 5 to 4 . 0
KMnOI
2.876Y (1 % Mn)
0.005 to 1 . 0
CoCll 6Hz0 KzCrnO7
16 1424 lus 2% HCl ?4% 2.2630 (0.8% Cr)
20
NiSOg. 7Hz0 Ni(NOd2. 6HzO MnCIz. 4Hz0
19.1479 plus 2% HzSOa (4% Ni) 19.9903 plus 2% “Os (4% Ni) 7.2055 plus 2% HCI (2% Mn)
10
0.005 to 4 . 0
Chromic anhydride
Water
0.006 to 4 . 0
Lead nitrate
Water plus 2% “ 0 3
0 . 4 to 4 . 0
Cobalt ahloride
Water plus 2% HCI
0 . 0 5 to 4 . 0
137
&)
5
50
10
100
Be Mn Ti Cr
LINEPAIRUSED 2927.82 2933.06
A.
;~;;:;~)Unrelolved 3067.73
2651 (6 unresolved linea) 2939.31 3383.765 3368.05 V 3093.13 Cr 3118.65 V 3130.270 Cr 3132.053 W 2589.2 Mn 2593.733 Fe 2382.034 Co 2378.62 Mo 2848.21 Cr 2849.83 Cr 3578.687 Ni 3524.543 Pb 3683.472 Ni 3619.393 Co 3453.514 Mn 3441.997
158
ANALYTICAL EDITION
VOI.
4,
KO.
3
of the element to be estimated). These data are presented graphically Mo % Be in Figures 2, 3, and 4. Table I indicates 0.005 0.5 the materials used for examination, the method of solution, 0.05 t h e concentration 0 26 range, and the line pairs measured. 0.25 The curves in Fig0.1 ures 2 to 4 may be used as standard or 0.50 calibration curves in the analysis of un0 06 knowns. The pro0.75 cedure in such an analysis is to prepare a solution as 0.006 1.0 indicated in Table I and, if the concentration of the ele0 0005 1.5 m e n t is a p p r o x i mately known, dilute the solutions to B A a concentration Of FIGURE2. CALIBRATION CURVESFOR FIGURE1. SPECTRUM PHOTOGRAPHS aPProximateb' that DETERMINATION OF PERCENTAGE OF of the center of the UNKNOWNELEMENTFROM DIFFERA . Variation of concentration of molybdenum with chroc a l i b r a t i o n curve ENCE I N LENGTHO F UNKNOWN AND mium 8s internal standard. B . Variation of Concentration of beryllium with menSTANDARD LINES ganese as internal standard. and photograph its Dotted lines are logarithm of continuous s p a r k Spectra. If curves. Nope of logarithm lines indicates conA condenser (0.005 microfarad) was shunted across the see- the concentration is which the line pair ondary terminals of the transformer. not approximately The solutions were prepared by weighing the quantity of known, solutions should be prepared by tenfold dilution, so pure material required to make a given volume of the most that each solution has one-tenth the concentration of each concentrated solutions used and diluting these with distilled preceding solution. Three or four such solutions will in water or other indicated solvent to yield the required con- nearly all cases cover the desired concentration range. To each solution is then added the iiildicated centrations. A known amount of the amount of solution containing the intersolution of the substance selected for nal standard and the spark spectrum is the internal standard was then added p h o t o g r a p h e d . In obtaining these to a definite volume of each solution and spectra the most dilute solutions should a photograph made of its spark spectrum. be photographed first and then the more (The photographs were taken on Eastconcentrated in the order of their inman 33 plates and developed with the creasing concentration. This procedure Eastman formula D-76 developer with reduces the possibility of contamination controlled conditions of temperature and of dilute solutions with the stronger solutime of development.) The lengths of tions. The minimum quantity of soluthe selected pair of lines were measured tion upon which the authors have made with a Bausch and Lonib plate magniobservations is about 2 cc. By the use fier containing a 20-mm. scale with of capillary tubing, however, it should which the length could be determined be possible to use micromethods and to within 0.02 mm. The lines selected obtain satisfactory analyses on 0.5 cc. for measurement conformed as nearly or less. The amount of unknown eleas possible to the requirements for homent in the solution is determined by mologous pairs as described by Gerlach measuring the lengths of the standard and Schweitzer (1). The difference in and unknown lines and subtracting the length of two lines will represent the standard from the unknown length; from ratio of their intensities, since by the the calibration curve it can be seen that use of a logarithmic sector the line denthis difference in length will represent a sities vary a t a logarithmic rate. The definite per cent of the element for which difference between the length of the Per Cent the analysis is made. line of the standard and the length of FIGURE3. CALIBRATION CURVESFOR I n Figure 2, the chromium, lead, and the line of the element to be estimated DE~ERMINATION OF PERCENTAGE OF cobalt curves are shown together so as was then plotted against the per cent of UNKNOWN ELEMENT FROM DIFFERENCE the element to be estimated (and also IN LENGTHOF UNKNOWN AND STAND- to indicate variations in the sensitivity range of the lines chosen for these eleagainst the logarithm of the per cent p" ARD LINES
us^^^
INDUSTRIAL AND ENGINEERING CHEMISTRY
May 15,1934
ments. As will be noted, the logarithm curves have different slopes which correspond in general to the s e n s i t i v i t y range, chromium having a narrow 2 range, lead a , medium range, while cobalt has the widest 0 concentration range -1 o ~ e rw h i c h t h i s -2 sp e c t r og r aplii c method of analysis 00 0 4 08 12 can be applied. Per Cent This range of useful FIGURE 4. CALIBRATION CURVESFOR c o n c e n t r a t i o n for DETERXTNATION OF PERCEYTAGE OF s pectrographic BERYLLIUM analysis is limited on 0 00 to 0 12 per cent in upper curve, 0 0 to 1 0 per cent in lower curve. the low concentration side to the intrinsic intensity of the line and its ability to produce a reasonable photographic image, on the upper side by the point where the logarithm of the concentration plotted against the 0 00
0 04
0 08
018
%
159
difference in line length ceases to follow the straight line obtained for the lower concentrations and begins to approach a constant value. Within this working range of concentration the error of observation was less than 5 per cent of the observed value. While this is a rather large error where concentrations greater than 1 or 2 per cent are concerned, the value of the method increases for more dilute solutions where the error in determination of a solution containing 0.01 or 0.001 per cent of the element will still be less than 5 per cent of the observed value.
LITERATURE CITED (1) Gerlach and Schweiteer, “Chemische Emissionspektralanalyse,”
Leopold Voss, Leipeig, 1931. (2) Hamburger and Holst, 2. wiss. Phot., 17, 265 (1918). (3) Soheibe, “Spektroskopische Analyse,” Akademische Verlags-
gesellschart, Leipeig, 1933. 14) Twvman et al.. Trans. Ontical SOC.(London). 31. 169 (1930). .. ~
32, 1 (1931).’
(5, Twyman and Hitchen, Proc. Roy. Soc. (London), A133, 72
(1931). RECEIVEDApril 27, 1933 Presented before the Dlvision of Physical and Inorganic Chemistry a t the 85th Meeting of the American Chemical 80ciety, Washington, D. C., March 26 t o 31, 1933.
Covering Capacity (on Water) of Aluminum Bronze Powder JUNIUS D. EDWARDS AND RALPHB. MASON,Aluminum Research Laboratories, New Kensington, Pa. HE metallic flakes of aluminum bronze powder are characteristically different from the granular particles of nonmetallic pigments. They differ so much in shape, structure, and composition that the methods of examination and testing, well developed and standardized for other pigments, are in many cases inapplicable to the study of aluminum bronze powder. Aside from their flake-like shape and metallic base, the flakes differ from most granular pigments in having a film of polishing agent on their surface. This thin film, usually containing stearic acid as the major ingredient, modifies the appearance of the flakes and their general behavior when dispersed in a paint vehicle. The interfacial relations between powder and vehicle, as well as the size and shape of the flakes, play a part in the important phenomenon, known as “leafing.” For commercial purposes, it is customary to grade powders according to the approximate mesh size of the largest flakes. A standard varnish powder, for example, has all been through a 140-mesh screen or its equivalent. While a screen analysis may give some idea as to the major dimensions of the flakes, it tells little or nothing about their thickness (or thinness). Obviously, the thinner the flakes, the more flakes of any particular size per pound of powder. Furthermore, the thickness of flake will affect the leafing characteristics of the powder. During an investigation of the properties of aluminum bronze powder, the authors developed a method for measuring the average thickness of bronze powder flakes, which has been found very useful over a period of years. An outline of this method was first described in 1927 (1). Since then the method has been standardized in detail and technic of operation. The method depends on the assumption that if all the flakes in a given weight of poKder could be spread out in a film one
flake thick and packed close so as t o eliminate interstices between the flakes as far as possible, the thickness could be calculated from the area of the film, its weight, and the density of the powder. A film which approximates these conditions can be obtained by proper manipulation of the bronze powder on a clean surface of water. A shallow rectangular pan with a flat rim is used as the container for the water and two flat, rigid strips of glass or metal which act as barriers are laid across the width of the pan t o define the ends of the film of powder whose area is to be measured. When a weighed amount of powder is carefully dusted onto the water surface which completely fills the pan, it tends to spread out in a thin leafed film. The flat barriers, resting on the rim of the pan near each end, perform a very important function in “coaxing” the powder into a film one flake thick. The results of the measurement are expressed in terms of the area in square centimeters covered by a gram of powder and this value is termed the covering capacity. It should not be confused with the so-called covering power (square feet per gallon) of a paint. Langmuir (2) and others have shown how stearic acid alone can be spread out on water in a film one molecule thick, and the dimensions of the molecule estimated in this way. In this experiment the polar molecules of stearic acid are uniformly oriented with the carboxyl group directed towards the water interface. In the case of the polished aluminum flakes, the film of stearic acid, many molecules thick, appears to be oriented and fixed upon the flakes. The powder flakes in the present method are only partly wet by the water and float upon the surface. By moving the metal strips back and forth upon the side rims of the pan, the floating film of powder between them can be stretched and compressed much like a fabric until all the flakes have been brought into the water interface. The powder is then compressed by moving
