Edition
Analytical
Number 3
Volume 3
Two Hundred Reagent Chemicals-Good
and Bad’”
Edward Wichers, Aaron Isaacs, atld Irl C. Schoonover BUREAUOF STANDARDS, WASHINGTON, D. C.
Two hundred and thirty-six lots of reagent chemicals Following fairly extensive, URIKG the last few but not entirely systematic, years, the AMERICAN purchased by the Bureau of Standards in the period testing of reagent chemicals CHEMICAL S O C I E T Y , July 1, 1928, t o December, 1930, were examined for conformity to the specifications of the American Chemical in earlier years, the Bureau t h r o u g h its Committee on Society, or, in the absence of such specifications, for of Standards began in July, Analytical Reagents, has preconformity t o the requirements indicated by the 1928, t o t e s t a l l i t s p u r pared specifications for a producers’ labels. Although few of them were exchases of such m a t e r i a l s . considerable number of the cessively bad, a large proportion of the chemicals At that time 62 of the SOanalyst’s most important refailed t o conform fully to the requirements. CIETY’S specifications were in a g e n t chemicals. T h e s e Except for the small group of insoluble products, force in the annual contracts specifications purport to which was much more unsatisfactory than the others, let by the G e n e r a l S u p p l y provide carefully considered no striking differences in quality between various Committee. Up to Decemstandards of quality which types or groups of chemicals were noted. In general, b e r , 1930, t h e e n d of the are designed to meet the rethe chemicals examined conformed less satisfactorily period for which results of quirements of careful anat o the producers’ standards t h a n to the American tests are given in this paper, lytical work without making Chemical Society specifications. Considerable differ19 additional specifications excessive d e m a n d s on the ences were found in the success of the producers reprewent into effect, making a ability of the producer of resented in this review in meeting the requirements total of 81 specifications in a g e n t s , or necessitating exof the specifications or of their own standards. Reforce during part or all of cessively high prices for the liance on labels as a definition of quality would not the 21/2-year period. reagents. Furthermore, the have been fully justified for any of the brands and would T h e p u r p o s e of t h e specifications c o n t a i n comhave been very unsafe for some. Bureau’s testing of reagent plete methods of test, which The results indicate the necessity for the continued chemicals is twofold. The are much more quantitative development of adequate quantitative methods of work is done both as a matin character than any which test, the critical use of such tests by numerous inditer of s e l f - p r o t e c t i o n , to have a p p e a r e d in s i m i l a r viduals so as to insure and confirm their adequacy, i n s u r e t h e work of t h e standards. For these reasons and the consistent application of the improved standa n a l y t i c a l laboratories so and because producers generards and tests by producers, under the stimulus of far as possible from faults ally have shown themselves the interest and demands of consumers. caused by poor r e a g e n t s , willing to sell their materials and t o gain i n f o r m a t i o n on the basis of the specifications in question, these new standards of quality offer an ex- about the purity of reagents on the market which may cellent common ground of understanding for the producer and be useful in helping to improve the quality of the mateconsumer of reagent chemicals. Up to date about one hun- rials available for the American chemist. Although the dred specifications have been adopted by the SOCIETY, covering total number of lots of material (236) on which this report is most of the reagents in very general use, and representing in based is not very large, the number is sufficient to throw some value probably much more than 75 per cent of the cost of all light on the general question of the purity of present-day rechemicals bought for analytical use. Of approximately agents. $23,000 reported .as spent for reagent chemicals bought Classification of Chemicals Tested by Types during the fiscal year 1930 by government laboratories in Washington from the Schedule of the General Supply ComThe 236 lots of material include 173 bought under the mittee, 84 per cent was for the 74 items which were purspecifications, which will be referred to as Group chased under AMERICAN CHEMICAL SOCIETYspecifications. SOCIETY’S I, and 63 bought on the general specification “analytical re1 Received May 7, 1931. Presented before the Division of Physical agent quality,” to be known as Group 11. Some of Group I1 and inorganic Chemistry a t the 81st Meeting of the American Chemical are materials for which specifications came into effect during Society, Indianapolis, Ind., March 30 t o April 3, 1931. * Publication approved by the Director of the Bureau of Standards the 21/2-year period but were not in effect a t the time of purchase. For this reason a few items are represented in of the U. S . Department of Commerce
D
228
ANALYTICAL EDITION
both groups. All told, the 236 lots of material represent 93 different reagents. Group I represents 61 items, with purchases for individual chemicals ranging from one to twelve lots. Group 11 represents 36 items, with a maximum of 8 lots of a single material. Tests of chemicals in Group I were, of course, made according to the requirements and methods prescribed by the specifications. Materials in Group I1 were tested for conformity to the producer’s own standards-that is, the labels on the containers. The labels of one producer are stated to represent actual analyses of the contents. For the purposes of our records, however, they were regarded as indicating maximum limits of impurities, the practice followed by the other producers whose materials were tested. That is, a material supplied by this producer which was better in one or more respects than the label indicated was not classified as unsatisfactory, although it may not have been correctly labeled. The methods used in testing Group I1 were taken from various sources, such as Krauch (3) or Murray (4), or the published methods of the producers. Any classification of reagent chemicals is necessarily arbitrary. However, dividing them into certain broad groups may be justifiable. Partly in order to furnish a basis of comparison with the purity of reagent chemicals some years ago, the grouping adopted by Buc ( 1 ) is followed in this paper. Accordingly, the chemicals are listed in Table I under the following types: liquid inorganic chemicals; liquid organic chemicals; soluble compounds of ammonium, potassium, and sodium (ammonium hydroxide is included with the “liquid inorganic chemicals”) ; other soluble salts; and insoluble products. The chemicals are divided into three classes: Class A represents those that conformed in all respects to the specifications, in the case of Group I, or to the label, in the case of Group 11. Class B comprises those chemicals which failed to conform to the specification or to the label in only one respect and by only a relatively small amount. Specifically, if a chemical contained not more than twice as much of one impurity as the specification permitted or the label indicated, it was placed in Class B. Class C comprises those chemicals which departed from the specification or the label in more than one respect, or in a single respect by more than 100 per cent. This method of grading is about equivalent to “good, fair, and bad.” To facilitate consideration the figures for the classes are given in percentages of the total number of lots tested in each group and type. Percentages do not mean much in cases in which only a very few chemicals were tested, but they are given throughout for the sake of uniformity. It will be observed that only 65 per cent of all the lotq of reagents bought in the 21/2-year period conformed strictly t o the standards, either the specifications or the producers’ labels. If the limits are liberalized so as to include the fair samples with the good ones, the percentage of acceptaLle materials is raised to 74. The percentage of samples conforming to the producers’ own standards (as indicated by the labels) is somewhat less than the percentage conforming to the SOCIETY’S standards. No doubt some allowance should be made for the fact that the materials in Group I1 are less commonly used and probably less important than those in Group I. Xevertheless, in view of general representation by producers that labels can be accepted a t their face value, a failure in reliability of 41 per cent should not be regarded too lightly. The relatively small proportion of chemicals in Class B, 10 per cent in Group I and 6 per cent in Group 11, as compared with 23 per cent and 35 per cent, reepectively, in Class C, indicates that for the most part the failure to conform to the standards is distinct enough not to be accounted for either by too rigid requirements or by uncertainties in the methods of test. Of course, Class C includes many de-
VOl. 3, No. 3
grees of inferiority. Relatively few of the chemicals examined, possibly 3 per cent of the total, might be termed “very bad.’’ The results of these tests are in fairly good general agreement with others made previously in this laboratory. Thirty per cent of 115 samples tested in 1922-23, representing nearly all of the reagents purchased during that period, were found unsatisfactory in one or more respects. From 1924 to 1926, 94 samples, representing the more important purchases, were examined, of which 18 per cent were unsatisfactory. T a b l e I-Classification b y T y p e s of C h e m i c a l s T e s t e d TYPE NUMBFR CLA?SA CLASS B CLASSC
%
70
%
40 36 55 34 8
73 78 66 65
-
25
7 14 7 14
20 8 27 21 75
173
67
10
23
..
.. 5 ..
1100
68 86
-
29
13
27 14 46 68
63
59
6
35
GROUP I
Liquid inorganic Liquid organic ”4, K , Na compounds Other soluble compounds Insoluble products Total
G R O U P I1
Liquid inorganic Liquid organic ”4, K , N a compounds Other soluble compounds Insoluble products Total
1 19 14 22 7
46
8
GROUPS I A K D 11 COMBIXED
22 14 24
30 67
__ Total
236
65
9
26
Buc ( I ) , reporting on chemicals purchased by the Bureau of Chemistry of the U. S.Department of Agriculture from 1915 to 1919, regarded 150 samples out of a total of 1300 examined, or 11 per cent, as “unsatisfactory,” as compared with 35 per cent placed in Classes B and C, or 26 per cent in Class C only, in this paper. Spencer ( b ) ,reporting on tests made in the Bureau of Chemistry from 1920 tQ 1923, stated that 32 out of 465 lots, or 7 per cent, were “returned as unfit for the Bureau work.” The natural conclusion from this comparison, that the general quality of reagent chemicals is a t present worse than in the years 1915 to 1923, is not supported by the experience of the average analyst. As a matter of fact, it is not unlikely that the reverse is true, certainly if only the period covered by BUC’Sreport is considered. The more probable cause of the difference is that both Buc and Spencer reported on routine tests which were made to determine whether the chemicals could be accepted for the wbrk of the Bureau and were interpreted somewhat liberally, whereas the tests reported in this paper were made to determine whether the materials purchased conformed to definite standards. A large part, but not all, of the rhemicals listed in Classes €3 and C were rejected. Furthermore, the improved methods of testing which have become available in recent years, mainly through the work of the Committee on Analytical Reagents, have made it possible t o determine the quality of chemicals much more quantitatively than could be done some years ago. Buc made comments on each of his five types of chemicals. His observation that the insoluble products were generally bad, pretty well describes the situation today, so far as can be judged from the very limited number of,samples examined. The quality of liquid organic reagents seems to be better now than it was in 1915-19. Now, as then, less complaint can be made about the common acids, alkalies, and alkali salts than about other inorganic compounds. Classification by Producers Inasmuch as nearly three-fourths of the chemicals under consideration were judged according to a common standard, it may be of interest to classify them according to the produc-
July 15, 1931
INDUSTRIAL A N D ENGl‘NEERING CHEMISTRY
229
ducers probably have not customarily tested for these impurities. Somewhat different are the cases of calcium carbonate containing 0.8 per cent of alkali chlorides and labeled “alkalies, 0.03 per cent;” and of seven lots of cobalt nitrate (an original delivery and six successive replacements) labeled “Ni, none, 0.05,0.20,0.075,0.24,0.24, and 0.03 per cent,” and containing 0.39, 0.46, 0.87, 0.50, 0.58, 0.58, and 0.07 per cent of nickel, respectively. In both of these cases the source of trouble lay in grossly inadequate methods of test. In both cases the producers are now acquainted with suitable methods and are in position to supply materials for which the impurities in question can be correctly indicated. These cases illustrate the opportunity that the user has of raising the standards by making constructive complaints t o the producers. In connection with the reference to calcium carbonate low in alkalies, it may be noted that while material satisfactory in this respect is now available, it is apt to contain an excessive amount of sulfate. Examples of materials which must have been tested very carelessly, if a t all, are as follows: tartaric acid labeled “nonvolatile matter, 0.007 per cent,” and containing 0.025 per cent (the SOCIETY’S specification permits 0.020 per cent) ; sulfurous acid labeled “non-volatile matter, 0.0001 per cent, sulfuric acid, 0.05 per cent;” and containing 0.0016 per cent and 0.63 per cent, respectively; arsenic trioxide (a primary standard) labeled “non-volatile matter, 0.05 per cent” and containing 0.4 per cent; and benzene marked “boiling point, 80.5” C.,” which had a boiling range of 80” to 92’ C. An extreme instance was that of bromine containing 6.3 per cent of chlorine but labeled “chlorine, 0.10 per cent.” This may have been Table 11-Classification of C h e m i c a l s Teeted, b y Producers a simple blunder, as was undoubtedly the instance of sodium PRODUCERS NUMBER CLASSA CLASSB CLASSC nitrite which was about one-third potassium nitrite. Mis% % % GROUP I labeling of one lot of calcium carbonate as to alkali content 1 80 78 7 17 was attributed by the producer to a blunder made by con2 35 63 14 23 39 64 10 26 3 fusing two grades of material. 16 44 6 50 4 23 70 13 17 All others The greater number of less extreme cases which fall into Total 1% 67 10 23 Class C are best explained either by failure on the part of the GROUP 11 producers to exercise the constant analytical control which they claim, over their products, or by a combination of inadequate methods and insufficient care in the analytical control. Anyone who has had experience in the testing of Total 63 59 6 35 chemical reagents for small amounts of impurities knows GROUPS I A N D I1 C O X B I N E D that methods in this field have been none too good and that 1 78 80 5 15 2 63 52 14 34 even if an adequate method is a t hand, competent analysts 3 53 62 8 30 4 19 47 5 48 may occasionally differ considerably in their results. All others 23 70 13 17 It is exactly in the development of better methods, their Total 236 65 9 26 critical trial by numerous individuals, and their use by Table I1 shows a sufficient differentation between produc- producers in replacement of the more familiar, but less reliers to be of concern to the analyst. Although the relatively able methods, that the means lie for real improvement in the small number of lots tested may make the results less signifi- quality of reagent chemicals. cant than they appear, it seems evident that there were disBasis of Possible Improvement tinct differences in the success of the different producers in meeting the standards. It also seems that the strain of There can be hardly any doubt that most of a general meeting the SOCIETY’S specifications was in some cases less improvement in the quality of reagents can be accomplished severe than that of making what is behind the label conform only through the interest and activity of the users. It is t o what is printed on the label. manifestly cheaper to produce poor chemicals than good ones and the pressure of competition always has to be borne, no Discussion of Specific Cases matter how much a producer may be interested in the quality A few specific instances may help to indicate ways in which of his products. On the other hand, a cardinal principle of improvement might be brought about. It was surprising business is to supply what is demanded, and reagent makers to find, for instance, five out of six lots of sodium bicarbonate can and undoubtedly will produce good reagents if there is a failing to meet the specification with respect to impurities genuine demand for them. I n the abstract the analyst will indicated collectively as “calcium, magnesium, and ammonium always agree that his reagents ought to be good, especially hydroxide precipitate,” and limited to 0.01 per cent. The in these days when he is confronted with increasingly greater amounts found were from 0.03 to 0.05 per cent. Apparently demands for accuracy in his work, but in the concrete he is the cause of this discrepancy lies in the fact that earlier stand- usually like the cobbler who is too busy to shoe his own chilards did not include limits for magnesium, or, in some cases, dren-he seldom undertakes to analyze his own reagents. If for either magnesium or calcium. Hence some of the pro- every competent and responsible analyst would spend one
ers from whom they were received. There are a t present in the United States six principal concerns which are producing reagents. Probably none of these concerns manufactures, or perhaps even refines, all of the materials which it places on the market, but all of them offer a more or less complete line of chemicals for the quality of which they accept responsibility. Four of these six producers were represented either directly, or by jobbers, in the General Supply Committee’s contracts for reagent chemicals during the period for which this report is made. There is some tendency to specialization in chemicals, and each concern is apt to gain awards or contracts on its specialties. Partly for this reason, there was relatively little opportunity to compare the quality of particular chemicals from several sources. However, since the classification by types did not disclose any radical differences in quality between the different types, except for the very small group of insoluble products, it is believed that the classification by producers is not inherently unfair to any one of them. A question as to this point might perhaps be raised on behalf of the producer listed as No. 4, who is represented by only 19 lots. Since all of the materials tested were bought on a competitive basis, no differences in price levels are involved. In addition to the classification according to producers of the chemicals bought on the SOCIETY’S specifications, Table I1 also classifies in the same way the chemicals of Group 11. So far as it goes, this group offers a means of judging the degree to which the different producers met their own standards. For completeness the two groups are combined in a similar way, so as to offer a picture of any general variation in the reliability of the producers.
230
ANALYTICAL EDITION
half-day a month in the indoor sport of examining the latest delivery of one of his more important reagents and rejecting the delivery if unsatisfactory, reagent chemicals generally would soon be above reproach and the next generation of analysts would have good cause to bless their benefactors. More than one user, in reply to a question as to what is done with chemicals that are found unsatisfactory, has answered, in effect, “Oh, we throw them away and tell the purchasing agent to buy a new lot from another maker.” Incidentally, it may be added that, for the most part, producers have been found very receptive to constructive suggestions and very willing to replace unsatisfactory materials. It is often claimed that present-day reagents are as good as the users are willing to pay for and that any extensive improvement in quality would involve a prohibitive increase in price. There can be little doubt that some increase in the cost of the chemicals would result from any general improvement in quality. Whether the increase would be so large as to be prohibitive is another question. If the market for reagents should refuse to tolerate prices commensurate with improved quality, it would be different from the market for almost every other commodity. The importance of quality rather than price is emphasized when one compares the cost of the chemicals with the cost of the chemist’s time. Figures from four laboratories in Washington, obtained some years ago (W), showed that for a given period the cost of chemicals was 2.2 per cent of the salaries of the chemists who used them. It should be possible to make even the proverbially penny-wise purchasing agents see that some increase in this ratio would
Vol. 3, No. 3
be justified if the waste of time that results from reagents of poor quality could be avoided. Analysts whose work counts are willing to pay for quality in balances, burets, and beakers. They will also pay for quality in chemicals when they are convinced that quality is available. The question of cost for a limited number of very extensively used chemicals may have to be answered by providing special grades of these materials for specific uses. For the larger number of chemicals used in smaller quantities for a great variety of uses, it should be feasible to adjust single specifications to the quality demanded by the greater number and more important of such uses. An illustration of this is found in the reagent mineral acids, which are produced in large quantities a t a high level of quality and a t prices which do not prohibit their use for a great many purposes, for some of which materials of lower quality could well be used. Single grades of these materials a t fairly high levels of quality are more economical than numerous grades. Literature Cited (1) Buc, H.E.,J. IND. END.CHBM.,11, 1140 (1919). (2) Collins, W. D., “The American Chemist and His Reagents,” unpublished address before the Lehigh Valley Section, of the American Chemical Society, Easton, Pa., September 23, 1925. (3) Krauch, C., “The Testing of Chemical Reagents for Purity,” 3rd ed., Van Nostrand, 1902. Translated by J. C. Williamson and L. W. Dupre. (4) Murray, B. L., “Standards and Tests for Reagent Chemicals,” Van Nostrand, 1927. (5) Spencer, G.C., IND. ENG.CKBM.,16, 1281 (1923).
A Degree Brix-Total Solid Relationship’ Study of Possible Theoretical Brix Correction Factor for Approximation of Solids by Drying Using Carbonate Ash Determination R. H. King COLLEGE O F AGRICULTURE, UNIVERSITY
An investigation involving 1870 samples of final molasses from 31 sugar-producing factories covering a 2112year period has been conducted in order to obtain a possible correction factor for Brix solids so that approximations could be obtained for true total solids. Average relationships between carbonate ash, Brix solids, and total solids by drying have been obtained. The difference between the Brix solids and the total solids has been evaluated and correlated with the carbonate ash content. Through the use of a correction factor based upon the carbonate ash, a close approximationof the total solids can be obtained.
O F THE
PHILIPPINES, LAJUNA,P. I.
The relationship between solids by drying and the Brix solids appears to be that of a straight-line function. Total solids may be approximated from these average curves if the carbonate ash content is known. However, if the ash content is not known, the graphs are of value in determining the probable total solids from the Brix solid determination. I t is suggested that carbonate ash determinations be us,ed in connection with Brix solids for the evaluation of the total solids in the chemical control where closer approximatiofis are desired for control purposes.
...... ...... HEMICAL control in cane and beet sugar factories is generally based upon the data obtained with a hydrometer known as the Brix spindle. This hydrometer in pure sugar solutions gives the actual solids in solution. I n such pure solutions the Brix solids are the so-called true solids, obtained by drying. However, as the non-sucrose material, such as ash, acids, and organic non-sugars, do not influence the hydrometer in the same degree as sucrose, errors enter into the control work when the degree Brix is used instead of the true solids obtained by drying. A quick ready method of estimating the true solids from the Brix solids is desired. Total recovery, sugar distribution,
C
1
Received October 7, 1930.
and the efficiency of the particular factory depend upon the estimation of the dry matter entering the process. The element of time and the expense of obtaining actual solids by drying prohibit an accurate control. It is well known that the character of the non-sugars, generally inorganic (2, S), governs the difference between the actual solids and the degree Brix. If ash determinations on average samples of molasses would give a correction factor, then ash determinations could be made in routine control work, and this correction factor applied to the Brix reading would give, at least, a closer approximation of the true solids. The advantage would be that the unsatisfactory method of drying in vacuo would be eliminated.
