T H E J O U R N A L O F I N D U S T R I A L -AND EhrGINEERIiVG C H E M I S T R Y V O ~ 12. . ;NO.
I020
During the present season Roland E. Kremers, who carried out a number of distillations for the Station, has collected and cohobated the aqueous distillates of wormwood, tansy, peppermint, and milfoil. The aqueous distillates of Monardn punctata and M . jistulosa will be collected by D. C. L. Sherk, who will also supplement Professor Miller’s study of M . $stuZosn by a parallel examination of M . punctnta. If i t required years of study to isolate and identify the oily constituents of plants, it will, no doubt, require years and years to study their water-soluble volatile constituents. If for years the writer has desircd to devote to these latter constituents such attention as they seem to merit, he has also wanted, for the same length of time, to study those products which escape from the condenser and tire not collected either in the separated oil or in the aqueous cohobate. The study of these escaping vapors will require, as experience has already shown, specially constructed condensers and absorbers. Thus will be trebled in size, as it were, this one field of phytochemistry. I n bringing to your attention some of our milling and distillation problems, the writer has not attempted to solve any milling or distillation difficulties from a technological point of view, but has desired to point out how large technological operations and the biochemical study of plants should work hand in hand for the advancement of plant chemistry.
*
A COMPARISON OF ACCURACY IN ANALYSIS OF METALLURGICAL MATERIALS DURING THE PAST TWENTY-FIVE YEARS By E. D. Campbell and George F. Smith UNIVERSITY
MICHIGAN, ANN ARBOR,MICHIGAN Received June 5, 1920
OF
It has been only a little more than j o years since steel manufacturers realized the necessity of chemical control of their finished product, and the consequent necessity of knowing the composition of the various materials entering into the process, and the changes taking place during the various steps between the raw materials and the finished steel. During the 70’s and ~ o ’ s chemists , of many metallurgical companies developed a practice of exchanging carefully prepared and analyzed samples of steel and ores, in order to compare the accuracy of the results obtained by different chemists working on the same sample. In February 1889, the late John W. Langley, in an address before the Engineering Society of Western Pennsylvania, advocated the preparation of a set of steels which should be analyzed by a number of leading chemists in different countries and should then constitute international standardsteels. This idea Langleydeveloped in a second paper.1 Committees on analysis were formed in England, Sweden, the United States, France, and Germany. Some preliminary bulletins were prepared during the next three years and the results of the analyses, representing the work of the committees from the first three countries named, were published in the Chemical News for September 29, 1893. I t was the intention of the American committee, when the results of the analyses had been collected, to have the principal part of the American portion of the five international standard steels kept in some suitable depository, so that small samples could be distributed to such chemists as might be entitled to them. The chemical laboratory of the University of Michigan was selected as a suitable depository and the five standard steels were deposited there in September 1893. Very little of this material was ever called for, and recently a large bottle of each of the five original international standard steels was sent to the Bureau of Standards t o be kept because of their historic interest. Although analytical chemists continued t o feel the need of 1
“International Standards for the Analysis of Iron and Steel,” Trans.
Am. Inst. Mining Eng.,October 1890.
IO ,
some means of determining the accuracy of analytical methods, and the variations which might be expected between different chemists working on the same material, it was nearly ten years later that the Bureau of Standards a t Washington instituted a system of preparing carefully analyzed samples, which would cover a wider field than that of steel alone. I n the summer of 1895 one of the authors gave a paper before Section C of the A. A. A. S. on “A Proposed Schedule of Allowable Differences and of Probable Limits of Accuracy in Quantitative Analyses of Metallurgical Materials.”’ The following quotation outlines the object and method of arriving a t the values shown in Table I, which are taken from a longer table in the original paper: Many methods for the determination of the various dements usually met with in metallurgical work have been proposed, each having its own claim for accuracy, or rapidity, or both, but as will be seen from the efforts of the international committee on the analysis of iron and steel, we are far from having perfect methods for metallurgical analysis. There are many sources of error in ordinary quantitative determinations, which, while they can be partially avoided, can never be wholly overcome. Among these may be mentioned such errors as arise from solubility of precipitates, solubility of apparatus in which operations are performed, impurities in chemicals, inaccurate graduation of volumetric apparatus, unavoidable error in accuracy of weighing, and last, but not least, errors due to what may be termed the personal equation, the presence or absence in the operator of that manipulative skill which distinguishes an expert from a clumsy worker. Since we cannot expect absolute agreement in results, it may be asked how close should quantitative determinations agree? This question cannot be answered by a single figure, since the unavoidable errors in the various determinations differ according to the element determined and the method used in the analysis. Just how great a difference between determinations should be allowed and what the probable limit of accuracy which may be hoped for, is largely a matter of judgment based upon the examination of the results obtained by different chemists, known to be careful operators, working upon the same material. Basing our judgment upon the usual errors of analysis, upon the commercial requirements of accuracy and upon the unavoidable sources of error we would propose the following schedule of allowable differences and of probable limits of accuracy for discussion in the section. I n the table below the first column shows the element or constituent determined; the second, a formula for calculating the difference which might be reasonably expected between the results of two chemists working upon t h e same material, and the third column shows a formula for calculating the probable minimum error which may be hoped for. TABLEI Allowable Difference of Per cent Iron and Steel GraDhitic carbon.. i 10.050 (0.02 X Cg)] Combined carbon in cast iron.. . . k [O.OSO f (0.02 x CC)] Carbon in steel.. , . k 0010 (0.02 x C ) l Silicon, . . . . , . . . i t0:005 (0.02 X Si)] Sulfur, . . . . . . . . k [0.003 (0.03 X S)l Phosphorus, . . . i [0.002 (0.02 x PI1 Manganese in cast iron and steel.. i [0.005 4-(0.04 X Mn) I Nickel.. . , . , . . . , , , k [O.OSO (0.02 X Ni)] ELEMENTOR CONSTITUENT
. . . .. . ... . Silica. . . . . . . . . . Alumina. . . . . . . Iron. . . . . . . . . . Manganese . . . . . . . Calcium oxide. . . . Magnesia. . . .. . . .. Phosphorus.. , . . .
+ + + ++ +
Probable Limit OF Accuracy
f [0.005
+ (0.005 X C g ) 1
,
,
Phos. pentoxide.
..
The object of the present paper is to bring out, by comparison of variations computed from the table with those actually found by skilled observers working on the same sample, the desirability of some such formulas for comparing the work of different analysts, and to emphasize the fact that the proportionate variations in the determination of elements, especially those occurring in small quantities, are larger than is generally realized. Undoubtedly the most valuable data for such a comparison are those given in the certificates of analyses issued by the Bureau 1
J A m . Chem SOC.,18 (1896), 3 5 .
Oct.,
1920
T H E J O U R N A L O F I N D U S T R I A L A N D E,VGINEERING C H E M I S T R Y TABI IN CAST IRON .E 11-SILICON DETERMINATION
-----
Allowable Difference of Per cent k [0.005 (0.02 X Si) 1
B. of S. Certificate B . of s. Value SamDlc Iron B . . . . . . . . . . . . . . . . . . . 1.267 I r o n B 4 b . . . . . . . . . . . . . . . . 1.34 Iron B 4 a . . . . . . . . . . . . . . . . 1.37 Iron C . . . . . . . . . . . . . . . . . . . 1.720 Iron C 5 a . . . . . . . . . . . . . . . . 1 . 8 4 Iron C Sb., . . . . . . . . . . . . . . 1.84 Iron C 5 c . . . . . . . . . . . . . . . . 1.85 Iron E . . . . . . . . . . . . . . . . . . . 2.21 Iron D 6 a . . . . . . . . . . . . . . . . 2.57 Iron D f i b . . . . . . . . . . . . . . . . 2 . 5 9 Iron D . . . . . . . . . . . . . . . . . . .2 . 6 4 1 Method not stated. 2 HC1 dehydration.
Applied .. k0.030 k0.032 + O 032 $0:039 ~0.042 i0.042 $0.042 10.049 1-0.056 - 0 057 i0.058
Probable Limit of Accuracy
+
--
+
Individual Observers Xaxinium and Deviation from Certificate Value--
Method A Drown’s Method
No. Observers
-0:07 +0.056 -0.044
11
+0:06
+0:03 f0.04
-0:03
f0.02 -0.03 f0.05 -0.03 4-0.05 -0.04 f 0 . 0 6 -0.06
..
..
‘4
..
+0.’040 -0:0201
, .
+0:04 t.0.06 +O.OZ +0.06 f0.04 +0.04
..
-0.02’ -0.06’ -0,031
-0.081
-0.041 -0.031
--i IO.002 f (0.003 X Si)]-
-
Method B Other Methods f 0 . 0 4 5 -0.03Z1 +0.03 -0.042
11 8 4 7 9 6
-0.02
r021
No. Observe1S 5 7
.. 5
..
5
9 4 6 5 5
Limit of Accuracy Formula Applied k0.006 f0.006 k0.006 r0.007 iO.008 kO.008 iO.008 50.009 10.010 iO.O1O r O 010
Proportion Observers Per cent within within Limit of 1,imit of Accuracy Accuracy 1/ 5
4/11 5/11 3/5 4/11 8/13 2/13 6/11 6/15 2/11 l/5
20
36 45 60 36 60 15 55 40 18 20
TABLE111-CARBON DETERMINATION IN STEEL Allowable Difference of Per cent k [0.010 (0.02 x C ) ] Allowable B. of S. Difference Certificate Formula B of S. Sample Value Applied ... Bessemer 8b 0.064 kO.012 i0.012 Acid 0. H. 0.1,. . . . . . . . . . . . 0 . 1 0 3 *0.012 Basic 0. H. 1 5 a . . . . . . . . . . . . 0.111 k0.014 Bessemer 96. . , . . 0.184 i0.014 Acid 0. H. 19a . . 0.207 k0.014 Acid 0 . II. 0 . 2 . . . . . . . . . . . . . 0 . 2 0 8 10.014 Basic 0. H. 1l b . . . . . . . . . . . . 0.211 10.014 Basic 0. H. l l a . , . . . . . . . . . . 0 . 2 2 5 -co.o15 0.242 Basic 0. H. io.015 Bessemer 912 0.254 10.016 Ni Steel 33., 0.278 1-0.016 0.290 i0.017 0.350 V Steel 2 4 . . . . . k0.017 0.364 Cr-Ni Steel 32. k0.017 Basic 0. H. 1 2 e . , . . . . . . . . . . 0.372 k0.017 Bessemer lob. . . . . . . . . . . . . . 0.373 i0.017 Cr-V Steel 30. . . . . . . . . . . . . . 0 . 3 7 3 kO.018 0.377 Acid 0.H. 0.4 kO.018 Acid 0. H. 20e.. . . . . . . . . . . . 0.392 i0.018 Basic 0. H. 12b. . . . . . . . . . . . 0.409 i0.019 0.436 Basic 0. H. 0 . 4 . . k0.019 0.453 i0.022 0.578 i0.022 0.581 20.022 Acid 0. H. 0 . 6 . . ........... 0.591 k0.022 Bessemer 22.. . . . . . . . . . . . . . 0 . 5 9 2 i0.022 0.599 Cr-W Steel 31. k0.022 Acid 0. H. 21a 0.617 k0.026 Bessemer 2 3 . . . 0.805 20.026 Basic 0. H. 1 4 a . . . . . . . . . . . . 0.815 i0.027 0.84 Acid 0. H. .34.. . . . . . i0.030 0.998 Basic 0. H. 1 6 a . , . . . . k0.031 Acid 0. H. 3 5 . . . . . . . . . . . . . 1.03 10.031 Basic 0. H . 1 . 0 . . . . . . . . . . . . 1.049 7----
+
7
+
____-
..
7
+0:007 f0.021
d
6
f0.005
9
9
+o.o14
+o.n17
4 -0.006 -0 om
9 6 3
7
10 8 6
C0.009
-0
01.5
7
8
9
6
..........
+0.016
-0,009
+n 019 -o
018
6
-0.014
of Standards. Through the courtesy of the director of the Bureau, a complete set of these certificates has been received by this laboratory. These certificates extend from 1906 to 1919,inclusive, and may fairly be taken as representing the best practice during these years. All certificates, to the certificate value of which five or more observers contributed, and which were applicable to the above table, were included in the comparisons following. In order to make these comparisons, itemized tables were made out for each element: six for the elements in cast iron; six for those in steel; and eight for iron and manganese ores. Each itemized table represents from 2 to 34 different samples, with not less than five observers reporting on each sample, while in S I X cases reports were submitted by more than 20 observers. The reason for the absence in the original table of formulas for computing elements so commonly found in alloy steels is easily seen in the date of publication, since a t that time nickel steels were about the only ones in general use. From the itemized tables, summarized tables were made up, the method of computing the average values and deviations being similar to that used by the Bureau of Standards in computing certificate values, since the number of observers reporting each value was taken into consideration. The descriptive heading of each itemized table shows the element determined and the formula for computing the allowable difference of per cent and the probable limit of accuracy. The different columns of the table represent: first, the Bureau of Standards sample with number; second, the certificate value;
+0:013 +0.014 f0.006 +0.018
-01017 -0.015 -0.003 -0.010
+0:009 4-0.009 $0.010 +0.010 fO.010 +0.013
-0:OlO -0.009 -0.017 -0.006 -0.008 -0.019
+0:009
-0:017 -0.010 -0.010
...
+0.005
+0.01 fO.010
8 7
+o.ni
4
+0.026
..
7 6 6 1
4
‘5 7 5 7
...
-0:019 -0.014
+0:006
Observers
-0.017
f0:023 +0.018
+o.oos
9
? +O.Oll
-0.012
+O.Oll
10 9
...
+0:008 -i-0.022
...
9
-01003 -0.010 -0.007
NO. I
...
-0:004 -0.014 -0.01 -0.007 -0.02 -0.018
Probable Limit of Accuracy 7 - i : [0.002 (0.003 X C)]Pronortion Per cent Limit of Obiervers within Accuracy within Limit Formula Limit of of Applied Accuracy Accuracy
+
-
Individual Observers Maximum and Deviation from Certificate Value--------Method B No. Method A Solution and Direct Combustion Observers Combustion
1 6 6 3 ,.
1 3 6
6 5 5
9
f 0 : 002 io.002 io.002 10.003 10.003 1-0.003 k0.003 i0.003 i0.003 10.003 i0.003 k0.003 i0.003 k0.003 10.003 k0.003 f0.003 i0.003 i0.003 f0.003 kn.003 f0.003 k0.004 -10.004 k0.004 k0.004 k0.004 k0.004 k0.004 10.004 + o 005
I0:oOs
+o.oos io.005
..
8/ii ,3/10 5/12
5. 7
til; 1/10
8 10 77
30 42 I1
3 1 ;
58
4/11 10/14 3/11 4/10 3/13 5/13 .5/12 5/15 3/14 2/1 I 4/ 9 6/ 9 3/11 1/12 I/ 8 2/13 4/12 4/12
36 71 27 40 23 38 42 33 21
6/10 6/ 9 4/12 7/13 2/14 4/13 1/12 5/13
18
44 67 27 8 13 15 33 33 60 67 33 56 14 31 8
46,
third, the allowable difference computed by applying the formula to the certificate value. The next four columns show the maximum and deviation from the certificate value with the number of observers reporting on each method, where more than one method was employed. In general, when more than one method was used, t h a t which was most popular, as shown by the number of observers, is designated “A,” while the next in number of observers is called “B.” The eighth column shows the probable limit of accuracy computed by applying the formulas to the certificate value. The ninth column shows the fractional proportion of the total observers whose values come within the probable limit of accuracy, while the last column expresses this same value in per cent. As silicon in cast iron and carbon in steel are two of the most frequent determinations required of steel-works chemists, the itemized tables (Tables I1 and 111) for these two determinations are given as being typically representative of all. In Table IV are shown the summarized results of these values. The first column shows the number of samples included in the itemized table from which the summarized values are computed. The second column gives the element determined, the third the range of certificate values in per cent, the fourth the average value, and the fifth the average allowable deviation computed by applying the formula to the average per cent. The next and four columns show the averages of the maximum deviations from the averages, together with the average number of observers by Methods A and B, as defined in describing the itemized tables. In the tenth column is given the average
+
-
+
T H E J O U R N A L OF 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 Vol.
I022
Ranse of Certificate Values in Per cent
No. StandElement ards Determined
TABLEIV-SUMMARIZEDRESULTSFOR CAST IRON AND STEEL Allowable Difference Maximum and Deviations from Mean Formula Certificate Value Cert. Applied t o No. ObNo. ObValue Cert. Value Method A servers Method B servers
+
Graphite C... . . . . 1.79 -3.27 Comhined C . . . . . . 0.38 -0.67 Silicon.. . . . . . . . . . 1.267-2.64 Sulfur.. 0.030-0.062 Phosphorus.. ..... 0.092-0.862 Manganese, . . . . . . 0.444-1.54
2.27 0.55 1.93 0.041 0.331 0.945
10.10 k0.06 f0.04 10.004 f0.009 f0.042
+0.05 fO.05 f0.004 +0.010 +0.016
34 35
Carbon . . . . . . . . . . 0.084-1.049 Silicon 0.003-0.303 Sulfur.. 0.019-0.103 Phosphorus 0.006-0.120 Manganese 0.154-0.918 Nickel . . . . . . . . . . . 1.62- 3 . 3 3
0.453 0.120 0.045 0.053 0.647 2.475
f0.019
+0.012
%
35 2
........... ......... ....... .......
f0.007 *0.004 f0.003
+0.030
fO.lOO
+o.o-i
4-0.006
f0.003 10.002 +O.Oll f0.035
TABLE V-IRON
DeterB. of S. Sample mination "Sibley" Iron Ore 27.. . . . . . . . . . . . Si02 Magnetite Ore 29.. ............... Si03 Crescent Iron Ore 2 b . . AlzOa Magnetite Ore 29.. Fe "Sibley" Iron Ore 27.. Fe "Norrie" Iron Ore 28.. Mn Manganese Ore 2 5 . . Mn Crescent Iron Ore 26.. CaO Crescent Iron Ore 26.. YgO "Sibley" Iron Ore 27.. Magnetite Iron Ore 29.. .......... Pi06
........... .............. ........... ........... ............. ........... ........... ...........
.
B. of S. Cert. Value 0.75 12.02 1.03 55.75 69.11 0.484 56.36 2.64 3 -44 0.037 1.01
Allowable Difference Formula Applied kO.10 f0 . I 2 k 0.03 f0.19 f0.23 k0.05 k0.22 10.06 k0.08 k0.003
kO.025
-0.07 -0.05 -0.04 -0.004
-0.008 -0.012 Steel -0.013 -0.006 -0.003 -0.003 -0.011 -0.025
AND
7 . 6
7 5 7 9
...
+0:04 4-0.004 f0.006 +0.013
-0.04 -0.004 -0.006 -0.023
'6 6 5 4
f0.012 f0.007 f0.004 f0.002 f0.027
-0.012 -0.007 -0.004 -0.003 -0.024
6 6 7 4 6
...
..
. . I
t o Mean
Proportion Observers within Limit of Accuracy
IO
Per cent within Limit of Accuracy
10.016 10.008
?0.006
31/ 83 27/ 82 42/111 70/lfi2 37/ 98 58/ 98
k0.003 kO.002 fO.OO1 k0.0005 kO.004 kO.017
138/395 154/369 244/485 122/301 97/313 13,' 18
fO.008 10.001 kO.002
37
33 38 43 38 59 35 42 50 40
31 72
MANGANESE ORES
-
+
Individual Observers Maximum and Deviation from Certificate Value No. ObNo. ObMethod A servers Method B servers fO.ll 4 . 0 7 21 f 0 . 0 9 -0.06 5 f 0 . 0 4 -0.03 9 +0:07 -0103 f 0 . 0 8 -0.10 6 .. f0.11 -0.26 9 19 +0: 20 d : l 8 f 0 . 0 3 6 -0.044 24 .. fO.09 -0.27 5 +0:27 4 : 2 0 11 4-0.26 -0.19 25 f 0 . 3 2 -0.22 25 .. 4-0.004 -0.002 22 .. fO.01 -0.00 5 ..
probable € h i t of accuracy computed by applying the formula to the average per cent. Column 11 gives in fractional proportion the number of all observers coming within the probable limit of accuracy, while in the twelfth column is shown the same value in per cent. As comparatively few iron and manganese ores have been analyzed and certificates issued, the results of those determinations on which five or more observers have reported are given in Table V, which has been prepared by substantially the same system as that used to show the values for iron and steel. A study of the results given in Table I V shows a very satisfactory agreement between the computed allowable deviation and that actually found by drilled workers in the case of the carbon, silicon, phosphorus, and sulfur, and the fact that considerably less than half of these experienced chemists come within the probable limit of accuracy bears out the original conclusion that insistence on agreement inside the computed limit of accuracy would be unreasonable. The close agreement of the deviations actually found with those computed is dependent on an allowable difference of more than two per cent of the element de-
I
Limit of
.Accuracy Formula Applied
Na.
Cast Iron
10 10 11 11 11 11
.........
-
~
12,
..
..
.. ii
.. .. ..
.... ..
..
.. ..
Per cent Proportion of ObObservers within servers within Limit of Limit of Accuracy Accuracy 43 9/2 1 40 2/5 46 12/26 50 rt0.06 3/6 38 k0.07 11/29 ~0.005 16 4/24 25 k0.06 4/16 f0.013 4 I /25 8 2/25 fO.011 20 *0.0004 4/22 100 rto.0055 5/5
Limit of Accuracy Formula Applied 20.006 kO.017 k0.006
termined, a larger experimental difference than chemists usuaIiy realize. The two exceptions, manganese and nickel, indicate very clearly the result of the improvements which have been made since 1895 in the methods for determining these two elements. The bismuthate method for manganese was first published in 1895, while the dimethylglyoxime method for nickel is of much more recent origin. In view of the largely increased number of elements which metallurgical chemists are called upon to determine, there seems to be need of a schedule somewhat similar t o that given in Table I for computing allowable differences and probable limits of accuracy, but extended to take in all the elements determined, the formula being modified where necessary to bring the results in close accord with the best modern practice. If such a revised schedule were prepared under the supervision of the Bureau of Standards, and issued with the certificates accompanying the analyzed samples sent out, it would be of much service t o chemists in checking up the accuracy of their own work and in interpreting chemical specifications.
SCIENTIFIC SOCIFTIES
SIXTIETH MEETING AMERICAN CHEMICAL SOCIETY, CHICAGO, ILL.,SEPTEMBER 6 TO IO, I920 PROGRAM OF PAPERS GENERAL SESSIONS JULIUSSTIEGLITZ,Honorary Chairman. Address of Welcome. JOSEPH R. NOEL, President of the Noel State Bank and Vice President, Chicago Association of Commerce. Address of Welcome. W. A. NOYES, President, American Chemical Society. Response. THOMAS E. WILSON,President, Wilson & Co. The Value of Technical Training in the Reconstruction of Industries. A. S. LOEVENHART, Head of Department of Pharmacology of the University of Wisconsin. Chemistry's Contribution to the Life Sciences. H. P. TALBOT. Relation of Educational Institutions to the Industries. W. A. PATRICK.Some Uses of Silica Gels. W. A. NOYES. President's Address-Chemical Publications. AGRICULTURAL AND FOOD CHEMISTRY DIVISION C. E. COATES,Chairman T. J. BRYAN,Secretary Antitoxins a s Food Preservatives. 1.. EDWARD GWDEMAN. 2. MELVIN DE GROOTE The Solubilities of Vanillin and Coumarin in Glycerol Solutions.
A Study of the 3. HENRYA. SCHUETTEAND M. JOSEPHINE PRICHETT. Determination of Fat in Casein. 4. R. H. CARR. Do Greens Aid the Growth of Chicks in Conflnement? 5 . C. H. BAILEY. The Hydroscopic Moisture of Flour Exposed to Atmospheres of Different Humidities. 6. F. C. COOK. The Composition of the Tubers, Skins, and Sprouts of Three Varieties of Potatoes. 7, F. C. COOK. Pickering Bordeaux Sprays. 8. WILLIAMBRINSMAID.A Test for Annatto in Fats and Oils. (By title ) BIOLOGICAL CHEMISTRY DIVISION
R.A. GORTNER,Chairman
A. W. Dox, Sccretar3'
1. HOWARD B. LEWIS A N D GENEVIEVE STEARNS Diet and Sex a s Fac-
tors in Creatinuria in Man. 2 CARL 0 JOHNS AND A. J. FINKS. Nutritive Value of Tomato Seed Press Cake. (Lantern.) 3. D. B. JONES AND CARL0. JOHNS. Hydrolysis of the Coconut, Cocos nuctfera. (Lantern.) 4. CARL0. JOHNSA N D CHAS. B. F. GERSDORPBT h e Cohune Nut, Atlaleo cohune. (Lantern.) 5. CARL 0. JOHNS A N D HENRYC. WATERMAN.Some Mung Bean, Phaseolus aureus. (Lantern.)
of t h e Proteins Globulin of the Globulin of the Proteins of the
