I N D U S T R I A L A. N D E N G I N E E R I N G C H E M I S T R Y
July, 1933
(5) Bryant, W. M. D., IND.ENQ.CHEM.,23, 101.9 (1931); 24, 591 (1932). (6) ChipmanyJ., Ibid., 24, 1013 (1932). (7) Chopin, M., Compt. Tend., 188, 1660 (1929); Ann. phys., 16, 101 (1931). (8) Dennison, D. M., Astrophys. J.,62,8 4 (1925). (9) Dennison, D. M., Phil. Mag., (7) 1, 195 (1926). (10) Dixon, H. B., Campbell, C., and Parker, A., Proc. Roy. SOC. (London) A100, 1 (1921). (11) Eastman, E. D , Bur. Mines, Tech. Paper 445 (1929); Circ. 6337 (1930). (12) Eucken, A., Wien-Harms Handbuch der Experimental-Physik, Vol. VIII, Pt. 1 , pp. 437-63, Akademische T-erl:tgsgesellschaft, Leipzig, 1929. (13) Ibid., pp. 440-1, footnote. (14) Eucken, A , , Jette, E. R., and LaMer. V. K., “Fundamentals of Physical Chemistry,” pp. 89-91, McGraw-Hill, 1925. (15) Eucken, A., and Lude, K. v., 2. physik. Chem., B5, 413 (1929). (16) Eucken, A., hldcke, O., and Becker, R., ivaturwissenschaften, 20, 8 5 (1932). (17) Fowler, R. H., “Statistical Mechanics,” p. 61, Cambridge University Press, 1929. (18) Haber, F., and Tamaru, S.,2.Elektrochem., 21,228 (1916). (19) Hausen, H., Forsc-h. Gebiete Ingenieurw., 2, 319 (1931).
(20) (21) (22) (23)
823
Henry, P. S.H., d\-ature, 129,200 (1932). Henry, P. S. H., Proc. Roy. SOC.(London), A133, 492 (1931). Justi, E., Forsch. Gebiete Ingenieurw., 2, 117 (1931). King, F. E., and Partington, J. R., Phil. Mag., (7) 9, 1020
(1930). (24) Kneser, H. O., n’ature. 129,797 (1932). (25) Knoblauch, O., Raisch, E., and Hausen, H., Tabellen und
Diagramme fur Wasserdampf, berechnet aus der spezifischen Warme, R. Oldenbourg, Munich and Berlin, 1923. (26) Landolt-Bornstein-Roth-Scheel, Physikalisch-chemischen Tabellen, 5th ed., Springer, 1923-31. ( 2 i ) Ibid., 1st supplementary vol., p. 700. (28) Lewis. G. S . , and Randall. M . , “Thermodynamics,” p. 80, McGraw-Hill, 1923. (29) Mecke, R., 2. Physik, 42,390 (1927). (30) hlecke, R., Z . physik. Chent., B16,421 (1932); B17, 1 (1932). (31) Osborne, K.S., Stimson, H. F., Sligh, T . S., and Cragoe, C. S., Bur. Standards, Sci. Paper 501 (1925). (32) Partington, J. R., and Shilling, W.G., ”Specific Heats of Gases,” pp. 146, 209, Benn, 1924; IND.ESG.CHEM.,24,691 (1932). (33) Shilling, W. G., Phil. Mag., (7) 3, 273 (1927). (34) Shilling, R. G., and Partington, J. R., Ibid., (7) 6,920 (1928). (35) Wohl, K., and hlagat, hl., 2. physik. Chem., B19, 117 (1932). RECEIVED December 3, 1932.
Control through Spectroscopy E. S. DREBLOW.4ND A. HARVEY Adam Hilger, Ltd., 98 Kings Road, Camden Road, London,
T
H E great sensitivity of the spectroscopic method led to its use in chemical analysis in an early stage of the development of the subject, and since those days (especially in the last decade) a fair amount of work has been done on the development of methods useful analytically, but to date no great use has been made of spectroscopy for control purposes such as the routine testing of works products, materials, etc. This has probably been due partly to the fact that it has seemed necessary to perform a certain amount of exploratory work before deciding upon the methods most suited to the work in hand. The need for this exploratory work is diminkhing. There will always be a certain amount of preliminary work to do, such as the. obtaining of spectrograms of standard samples, etc., but this apparently unproductive initial labor is not necessarily n drawback. Trained spectroscopists are scarce and, in general, most people entrusted with a spectrograph for the purposes indicated will be encountering a new technic. The necessity for photographing the spectra of standard samples, etc., leads to a certain facility being gained before any serious analytical work is attempted, and this is an advantage. The value of spectroscopy for control purposes is coming to be recognized, and spectroscopic methods are being more employed in industry. While the authors know of many cases where this is taking place, in too few instances have the methods adopted or the results obtained been made public. There is thus a decided paucity of published material, but certain of the details regarding the actual use for control purposes of spectroscopy in three industries are known and are here reported. CABLE SHEATHIKG The British Post Office Engineering Department has specified that the lead sheathing of aerial cable must contain between 0.8 and 1.0 per cent antimony. Throughout this range the spectrograph furnishes a quicker and more convenient test than is possible by means of chemical analysis, LE.4D
N.W. 1, England
and because of this the department recommended (1) the adoption of the spectrographic test. Later work has shown that the method may also be employed for the estimation of cadmium and of tin in lead, and, since the exposure that gives the antimony line also yields the cadmium and tin lines, the speed of analysis is obviously increased. The actual technic adopted is that of the internal standard, the photometric side of the method being that originated by Scheibe and Keuhausser (3). This latter involves the use of a rotating logarithmic sector in addition to the quartz spectrograph employed for registering the spectrum. The sector is placed in front of the spectrograph slit, and its use results in the spectrum lines having varying lengths, these lengths being a logarithmic function of the intensities. In the internal standard method, which affords a simple means of compensating for small deviations in routine, etc., the intensity of a line of the minor constituent under estimation is compared with that of a line due to the main substance. The principle involved is that the ratio of the intensities of the two lines is dependent merely upon the relative concentration of the two elements, I n this instance two lines are selected, one being an antimony (or cadmium or tin) and the other a lead line. The relative lengths of the two lines are then studied as the concentration varies, and a curve is plotted connecting the two variables (4). Once this curve is obtained, samples of unknown constitution are immediately analyzable by reference to the curve. With regard to the practical details, a spark discharge is passed between two pieces of the sample. Three or four photographic exposures are made of this spectrum and the plate is developed in a normal fashion. The time of analysis is given (1) as 5 minutes for photographing the spectrum (three or four exposures), 5 minutes for development, and 5 minutes for measuring the plate. This presumes that other work is being carried on concurrently with the fixation, etc., of the plate. If this is not the case, the time from commencing the analysis to the final production of content figure is 30 minutes. Chemically, the estimation of the antimony
I N D U S T R I A L A N D E N G I K E E R I N G C H E 31 I S T R Y
824
\-(A 25, N o . 7
TABLEI. LEADIX BRASS Lead line:
A2446
A24i6
A2614
....
.... .... .... .... .... ....
B. V.a
LBAD % 0.005 0.01
.... ....
0;025
0.04 0.06 0.09 0.12
0.2 0.3
....
.... .... .... B. V.
0.4
5.0 5 Barely visible.
....
.... ,,..
.... .... .... ....
1.2
1.6 2.0 2.5 3.5
B. V.
.... ....
0.5 0.8
I\ 2858 cu .... . . . ....
;)I >
..
.... ....
cu
= 12407
>
content would likewise take about this time, EO that, unless cadmium or tin is also estimated, the spectrograph produces no marked saving of time. If, however, cadmium is estimated a t the same time, then, in view of the lengthy nature of the chemical analysis in this case, a considerable timesaving results. The leading cable firms in Great Britain are now employing this method for testing sheathing.
STEELS In the works of several English steel and related companies, visual instruments are being used for control purposes. Visual spectroscopy is less generally applicable than photographic but is considerably faster than the latter and possesses an accuracy high enough for the purposes. The instrument (the Spekker Steeloscope) is a two-prism glass spectroscope but is sturdily built so as to be suitable for workshop and factory use. The slit is protected by means of a glass lens, and the eyepiece slide clicks into certain definite positions, each of which is suitable for observing the presence or absence of a particular alloying metal in steel. The Steeloscope is being put to a variety of uses. I n some cases it is employed for the sorting of loads of scrap steel. In others it is used t o perform an analysis preparatory to heat treatment of the specimen. Possibly it is employed most frequently for the checking of bars of steel before they leave the works. If a bar of another alloy slips into a consignment by mistake, the spectroscope picks it out immediately. Without the spectroscope the first notice of such a mishap is most likely to come from the customer, and the results may be unfortunate! In steel F-arehouse practice, bars and rods 3 to 12 feet in length are run along three rails and come to rest on three concave rollers. At this point the observer (an ordinary steel warehouse laborer) drags the bar along the concave rollers towards the instrument. An upright rod of pure iron is then brought into contact with the bar under test and an arc is formed between the two specimens. Such use of spectroscopy is extremely rapid since it is not a question of detecting which metals are in the bar, but merely whether all the bars in the batch have the same content of, for example, nickel. A number of metals can be sought a t the same time-thus, chromium, molybdenum, copper, cobalt, tungsten, vanadium, manganese, and titanium can all be handled. If merely one metal is of interest, it should be possible to examine a batch comfortably a t the rate of one per minute. An outspoken report from an English steel firm (which employs several spectroscopes for control purposes) states concisely just how capable the Steeloscope is: What we regularly use the Steeloscope for, and what v.-e consider to be its most useful function, is to find foreign items or great
X3684
....
.... .... .... ...
B.v. ....
n. v.
='! cu > \ 2858 ....
=
>
i
.... ....
B. V.
....
3688 'CU
....
....
.... .... = < I> cu
> ) 4063
2 ) 2883 cu = . .
A4058
....
,
....
.... ....
A2873
>' ...
....
...
...
.... .... ....
....
differencesin a batch of material which is ostensibly all of the same class. This the apparatus does very well, in our opinion. The actual analysis of such foreign steel is best determined, if its exact composition is required, in a chemical laboratory. In normal working, sam les of steel in our steel warehouse are examined at the rate orabout one per minute where two elements (Ni and Cr) are in question, and about one in two minutes where a third element (Mo) is also involved. If some samples do not agree with the rest, they are put on one side, but the routine examination of the bulk is not suspended. The rejects are subsequently examined again, and if it is considered necessary, drillings are taken for analysis. If they are of some well-known class, however, they are simply returned to be stored with that class of material. The classes of steel which we normally examine spectroscopically are nickel, nickel-chromium, chromium, and nickel-chromemolybdenum steels. iiny samples not legitimately belonging to a batch can be picked out rapidly and with certainty; the class of steel t o which such rejects belong can usually be given, but we should not dream of asking the Steeloscope operators for the exact analysis.
COPPERAND ZINC ALLOYB Brownsdon and van Someren (2) have recently described the manner in which they have employed spectrography in the Imperial Chemical Industries metals works a t Birmingham, England, for the daily examination of metals and alloys. They do not attempt to obtain accurate figures for the concentration of the various impurities since they do not consider such accuracy necessary. They say, "a knowledge of the order of the concentration of an impurity is in many cases as useful to the metallurgist as a n analytical figure calculated to the second or third place of decimals." Since a knowledge of the order of the concentration is all that is required, a special technic is employed vhich enables the results to be obtained with great speed yet with an accuracy sufficient for the purpose in hand. Seldom is there a sharply defined limit of concentration above which the presence of an impurity becomes undesirable, but., since in practice it is necessary to work to a definite figure, some limiting concentration is stated and this figure is generally well wit'hin the margin of safety. The tests on the finished products, therefore, have merely to show that the concentration of the impurity is below a definite figure and the workers in question based their technic on this fact. A large number of analyzed samples was collected, and their spectra were photographed under standardized conditions. A study of the plates permitted a table to be prepared, showing the percentages a t which the various impurity lines appeared and a t which they were judged (by visual examination) to be equal in intensity to adjacent lines of the main substance. Once this kind of table has been prepared (this is t,he type of Iengthy preliminary work referred to in the introduction), when the spectra of samples of unknown composition are received, an examination of the plate (which
IKDUSTRIAL AND ENGINEERING CHEMISTRY
July, 1933
takes only a minute or so) gives the concentration of the impurity within the limits laid down by the table. Table I ( 2 ) illustrates the method. Considering the line (due to lead) X 2446, a t a concentration of 0.2 per cent in brass this line is barely visible, while a t 5.0 per cent it is of the same intensity as the copper line X 2407. At 3.5 per cent this lead line is a little weaker than the copper line X 2407, but a t that percentage the lead line X 2614 is equal in intensity to the copper line X 2618. I n general, it is obvious that the estimation of the concentration is not dependent merely upon one line, but that other checks are available. A diagrammatic representation of the spectrum ( 2 ) is also included in the paper (and would be prepared beforehand by anyone using the method) so that the various lines are immediately recognizable. The speed of the method is remarkable. A Hilger small quartz spectrograph is employed and the exposures per sample lie between 10 and 20 seconds. The length of slit employed is only 1.5 mm.; hence, twenty to twenty-five exposures are obtainable on a 4’/4 inch x 3l/4 inch plate. In exanlining brass, a rod of pure copper is used as one electrode, the sample forming the other. If we assume that twenty samples are being examined as part of a regular routine, then, allowing for the changing of the electrode in each case, probably an hour is consumed in photographing the various spectra. Development takes only 5 minutes, and the fixing, washing, and dry-
825
ing of the plate can proceed while other work is being performed. (Where analyses are required in the minimum time the plates can be examined wet, or they can be dried quickly by means of alcohol.) The impurities lead, tin, iron, nickel, aluminum, manganese, arsenic, and bismuth can all be estimated from the one plate. The examination of this plate takes 15 minutes so that as the result of less than 1.5 hours’ work it is possible to pass or reject twenty samples in each case with regard to eight different impurities. The speed of the method is thus exceptionally high, and the accuracy, although not high, is sufficient for work of this type. Gross blunders, such as occasionally creep into a chemical analysis, are difficult to make, and a permanent record of the analysis is available. ACHKOWLEDGMENT Table I was reproduced by kind permission of the Institute of Metals.
LITERATURE CITED (1) Brit. P. 0. Eng. Dept., Research Rept. 5651 (1931). (2) Brownsdon and van Someren, J. Inst. Metals, 46, 97 (1931). (3) Scheibe and Xeuhausser, 2. Angew. Chem., 41,1215 (1928); Twyman and Simeon, Trans. Optical Soc. (London) 31, 169 (1930). (4) Twyman and Harvey, J . Iron Steel Inst. (London), ildvance copy KO. 11 (1932).
RECEIVED January 5, 1933
CORRESPONDENCE ~
~~~~
Inversion of Sucrose by Invertase a t Low Temperatures SIR: The fourth column in Table I of the article appearing under this title ( 2 ) should read “Thawed at room temperature for 48 hours” instead of “98 hours.” Some 310 days after the last analysis recorded in Table 11, samples were removed and the results, which serve to complete and extend the data previously reported, are shown below. Some evidence of crystallization in the 68 per cent sugar solution was observed at this time, and therefore the results for these are probably somewhat high. The temperature of storage during this period remained sensibly constant at -18” C. These data show definitely that enzymatic action can occur even in the hard frozen state. Organoleptic examination of frozen fruits and vegetables confirms this. In addition, Onslow, Kidd, and West (3) reported that 1.5 per cent of the cane sugar
present in a frozen po-ivder of Bramley’s seedling apples was hydrolyzed in 7 months of storage at -20” C. Barker (1) found an average increase of 0.17 gram of total sugar per 100 grams of potato tuber powder stored at -20” C. for 7 months. He attributed this to diastatic hydrolysis of starch. LITERATURE CITED (1) Barker, J., Dept. S C L .Ind. Research R e p t . Food Investigataon Board 1930,78 (1931). (2) Joslyn, M. A,, and Sherrill, hf., IND. EXG.CHEM.,25, 416 (1933). (3) Kidd, F., Onslow, M.,and West, C., Dept. Sci. I n d . Research Rept. Food Investigation Board 1.930,52 (1931).
USIVERSITY OF C.ALIFORNIA BERKELEY, CALIF.
M. A. JOSLYN
M a y 2, 1933
READING AND PERCENTAGE TABLE 11. SACCHARIMETER OF SUCROSE INVERTED AT VARIOUSCONCENTRATIONS OF SUCROSE AND OF INVERTASE INITIAL SACCHARIMETER READINQ A N D INVERTASE INITIALCONCX. PER cc. -SACCHARIMETER OF S W A R O F SOLN. 11 13 M Q % %
.
65.8 68.3 66.8 59.1 61.1
..
.. ..
.. .. ..
a
d:7 6.9 9.7 Some crystallization of Sugar
1.6 0.2 0.5 3.8 1.2
.. ..
.. .. ..
READING AND PERCENTAGE SUCROSE INVERTED AFTER FOLLOWING NUMBER OF DAYS:25
.. ..
64.3 68.0 66.8 55.7 60.4
.. ..
49:3 52.7 53.9 45.3
:s.o
-6.8
. . 32.8 34.2 11.1 13.6
6:s 2.5 0.4 1.7 1.0 15.5 2.0 0.0 17.5 2.0
70:O 22.0 4.0 occurred during
27
%
..
..
.. .. .. .
I
..
-1.6 +6.0
+9.7 thawing.
53
%
55
%
115
%
5.0 .. , , 0.0 .. .. 1.0 . . .. 12.5 . . .. 10.0 . . . . 40.9 19:o . . 51.2 4.6 . . 53.9 0.4 . . 44.0 4.4 . . 46.0 0.9 . . 17.4 37.0 . . 31.1 6.5 . . 34.0 0.0 . . 7.2 38.0 13.0 6.2
1oo:o
38.0 6.3
.. .. ..
..
117
% 57.2 11.3 66.3 2.5 66.2 1.2 39.4 28.0 56.4 7.0
..
.. .. .. .. .. .. .. .. ..
.. .. ..
-2.5 1 o o : o 0.0 76.5 i 8 . 5 13.0
..
.. ..
..
425
%
..
.. ..
,.
23:2 43:5 46.5 10.8 54.0 0.0 38.7 12.5 45.2 2.0 -2.4 82.5 26.4 16.5 34.5 0.0 2.7 62.5 13.3 13.0
.. ..
..
427
% 39.0 31.Sa 60.8 8.20 63.5 6.0a 9.6 65.0 42.8 23.7
..
..
.. .. .. ..
..
-2.5 1oo:o -3.5 100.0 6 . 5 28.0
.... %..* . .. ..
.. ..
-2:o 79:5 36.8 24.5 52.5 4.0 23.2 38.2 43.0 5 . S -9.6 90.0 10.0 54.5 31.4 5.0 -3.0 92.0 9.0 5.0
..
.. ..
