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. Ind. 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 c c . -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
..
.. ..
