Jan., 1919
T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
ash silicates of t h e r a w mix carried over mechanically in t h e dust, a n d (c), in t h e case of coal-fired kilns, t o t h e ash of t h e coal which m a y yield u p a portion of its potash through t h e action of t h e lime in t h e dust. T h e first-mentioned source is ordinarily much t h e most important. 2-The water-insoluble b u t acid-soluble potash of cement dust is d u e ( a ) t o a recombination of a portion of t h e volatilized potash with t h e ash of t h e coal used for fuel, ( b ) t o a recombination t o a much smaller ext e n t , a n d only under certain conditions, with t h e siliceous material originally occurring in t h e r a w mix, a n d (c), t o a partial decomposition of t h e silicates of t h e r a w mix a n d also of a n y coal ash which is carried over mechanically in t h e dust. 3-The acid-insoluble potash in cement dust is d u e t o undecomposed silicates a n d coal ash carried over mechanically in t h e dust a n d t o a recombination of t h e volatilized potash with t h e ash of t h e coal when t h e a m o u n t volatilized is low.
45
4-The portion of t h e potash in t h e dust which has undergone recombination is of t h e nature of a potash slag or impure glass. When t h e a m o u n t of potash volatilized is low, a n d particularly in t h e presence of carbon, some recombination m a y take place with t h e siliceous material of t h e raw mix as well as t h a t of t h e ash. j-It is probable t h a t t h e extent of t h e recombination would be reduced if t h e burning of t h e cement were done under oxidizing rather t h a n reducing atmospheric conditions. 6-The extent of recombination would also probably be reduced by a n y procedure t h a t would introduce lime or sodium chloride into t h e dust a t t h e hottest part of t h e kiln. 7-The greater t h e a m o u n t of potash volatilized, t h e lower will be t h e proportion t h a t will undergo recombination in t h e dust. BUREAUOF SOILS
u. s. DEPT O F AGRICULTURE D. C. WASHINGTON,
LABORATORY AND PLANT RESULTS OF FURTHER COOPERATIVE WORK ON THE DETERMINATION OF SULFUR I N PYRITE CHECK SAMPLE NO. 4'
this latter method t o be much nearer t h e t r u t h , a n d while t h e discrepancy between t h e maximum a n d mini m u m results was rather wide, b y excepting a few By H. C. MOORE results, evidently extreme, t h e agreement was uniT h e July 191j a n d December 1916 numbers of THIS formly better. T h e purpose of t h e investigation covered b y this J O U R N A L contain reports of t h e cooperative analyses of pyrite for sulfur. This report m a y be regarded as cov- report was t o continue t h e work, using only one samering a continuation of t h e work described in t h e former ple, t o invite a larger number of laboratories t o participate, t o search for t h e weaknesses, if any, in t h e reports . T h e first two reports pointed out anew several sources Allen a n d Bishop Method, a n d t o acquaint a larger of error in this determination, especially in connection number of analysts with this method. There was a with t h e Lunge method a n d its various modifications. very generous response t o t h e invitation, a n d results T k e y also proved t h e Allen a n d Bishop Method t o be were received from thirty-nine (39) laboratories, inpractically free from these errors, a n d t h e results b y cluding t h e work of fifty-one (SI) analysts, as follows:' C. Clifton Howes J. M. Coleman W. E. Dickinson Gascoyne and Company Paul Rudnick (analysts W. J. Imig, R. A. Greene) T. 0. Holbrook Wilev and Comoanv F. F: Chapman' I,. C. Drefahl (results from eight (8) branch laboratories) P. R. Sabin W . R. Austin and F. K Wanner W . S. Allen (results of four analysts) C A. Butt E Fitzpatrick (results of two analysts) W . J. Rattle and Son A. Stanley Fox C. C. Nitchie V A. Moore Harry Johnson J. A Root Crowell and Murray W . D. Richardson (result of four analys C. B. McComas F. J. Bartholomew McCandless Laboratory M. H. Coblentz E. W. Magruder and J. H. Parkins C. N. Hoadlev
Davison Chemical Company Planters Fert. and Chem. Company International Agl. Corporation Gay Street Armour and Company Southern Fert. and Chem. Comoanv - . Gay Street E. I. du Pont de Nemours and Comp Grasselli Chemical Company
Baltimore, Md. New Columbia, Orleans, Tenn. La.
American Zinc Company of Illinois Tennessee Chemical Company General Chemical Company International Agl. Corporation Nichols Copper Company 501 Commercial Bank Building Aetna Explosives Company Mineral Point Zinc Company Armour Fertilizer Works Standard Oil C o m p a n y Anaconda Copper Mining Company 406-1 1 Perry-Payne Building Swift and Company Armour Fertilizer Works N. J. Zinc Company of Illinois Rhodes Building F. S. Royster Guano Company F. S. Royster Guano Company Mountain Copper Company Commercial Acid Company Ernoire Zinc Comoanv
E. St. Louis, Ill. Nashville, Tenn. Laurel Hill, N. Y. Atlanta, Ga. Laurel Hill, N. Y . Cleveland, Ohio New York, N. Y. Depue, Ill. Chrome, N. J. Bayonne, N. J. Anaconda, Mont. Cleveland, Ohio Chicago, Ill. Baltimore, 1Md. Palmerton, Pa. Atlanta Ga. Macon,'Ga. Norfolk Va. Martindz Cal. E st. Lobis 111. CHnon City,' COI. New York, N. Y . Atlanta, Ga. Atlanta, Ga. Atlanta, Ga. Atlanta, Ga. Atlanta, Ga.
1 Presented before the Fertilizer Division a t the 56th Meeting of the American Clhemical Society, Cleveland, September 10 t o 13, 1918.
Baltimore, Md. Chicago, Ill. Savannah, Ga. Baltimore Md. Wilmingtdn, Del. Cleveland, Ohio
1 N o t listed in the same order as given in the subsequent tabulation of results.
46
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
T h e sample used for this work, designated as Check Sample No. 4, is a Canadian pyrite. A large sample was ground t o pass a n 80-mesh screen a n d very carefully mixed for a considerable length of time so as t o insure uniformity. T h e sample was then spread out in a thin layer a n d individual bottles filled b y taking small portions from several places. The bottles were tightly stoppered and sealed. It is confidently believed t h a t t h e samples sent out were uniform a n d t h a t discrepancies in results are not d u e t o non-uniformity of samples. This opinion is confirmed in p a r t b y the results obtained b y five analysts in this laboratory on five separate sealed portions, which results appear in Table 11. This opinion is further confirmed by t h e fact t h a t the agreement between most of t h e laboratories familiar with t h e modified Allen and Bishop method is very close. T h e instructions accompanying the sample were as follows: INSTRUCTIONS FOR COLLABORATORS IN COOPERATIVE WORK ON THE DETERMINATION OF SULFUR IN PYRITE SAMPLE
The sample for this work is marked No. 4, is a sample of Canadian ore, and has been ground to pass an 80-mesh screen and requires no further preparation. MOISTURE
Dry 5 g. in an oven at
100”C . for
one hour.
SULFUR
and 3 parts carbon tetrachloride. Cover beaker, and after allowing to stand for 15 min. at room temperature, with occasional shaking, add I O cc. concentrated nitric acid and let stand a t room temperature with occasional shaking for 1.5 min. longer. Heat below 100’ (placing beaker on a piece of asbestos on top of the steam bath is convenient), until all action has ceased and most of the bromine has been expelled. Now place the beaker in the rings of the steam bath and evaporate to dryness. (Evaporation is greatly hastened by raising the cover glass with one or more bent glass rods.) Cover residue with IO cc. concentrated hydrochloric acid and again evaporate to dryness, keeping beaker covered as before. DEHYDRATE THE SILICA by leaving the beaker on the steam bath, or in an air bath at 100’C. for from */2 to I hr. EFFECT SOLUTION by moistening the residue with I cc. concentrated hydrochloric acid followed by 50 cc. hot water and rinse down cover, riders, and sides of beaker. Remove riders, replace cover glass, and warm until solution is complete. Then allow to cool for about 3 min. REDUCE IRON by adding 0.1g. of powdered aluminum and shaking beaker (covered) t o thoroughly mix with the liquid. (Sufficient aluminum powder must be added for complete reduction of the iron but any considerable excess is to be avoided. Subsequent filtration is facilitated by having the excess aluminum small.) When reduction to ferrous iron is complete, as indicated by the color of the solution, and the latter has cooled sufficiently so that no “misting” is noted in the beaker, rinse down cover glass and sides of beaker. FILTER to remove insoluble matter, or excess aluminum powder, through an 1 1 cm. or 1z1/2 cm. paper (B and A, grade A, S and S 590, or Munktell No. 0) into an 800 cc. beaker and wash the residue thoroughly with hot water. DILUTE the filtrate to a volume of 650 cc. with cold water,
11,
No.
I
add z l / z cc. concentrated hydrochloric acid, and stir to mix thoroughly. PRECIPITATEsulfate by adding 50 cc. of cold 5 per cent barium chloride solution, without stirring, and in single drops at the rate of about 5 cc. per min. A precipitating cup, designed by Allen and Bishop, or a capillary tube connected to a burette or suitable container is convenient for this purpose. When the barium chloride has been added, mix the solution by stirring, and let settle for z hrs. or, preferably, over night. FILTER through a No. 4 porcelain Gooch crucible (35 cc. capacity) having a fixed bottom and packed with a thick layer of asbestos. After the clear liquid has run through the filter, rinse the precipitate into the crucible by means of a stream of cold water, thoroughly police the inside of the beaker and after transferring all of the precipitate wash 6 times in the crucible with cold water. DRY THE PRECIPITATE in the drying oven for about ‘/z hr. A longer period of drying is a protection against breaking the crucible during the subsequent ignition, also against spattering of the precipitate. IGNITE THE PRECIPITATE by heating the crucible in a moderate flame for a minute or two, then igniting to constant weight over the full flame of a Fletcher, Meeker, or similar burner, or in an electric furnace a t 1600’ F. THE PER CENT OF SULFUR is found by dividing the weight in grams of barium sulfate by 4 and multiplying by 100. NOTE-An electric hot plate, having suitable temperature control, is a convenient substitute for a steam bath, but the surface temperature of the plate should not much exceed 100’C. else some of the free sulfuric acid is lost by volatilization. METHOD 11-Follow your usual methods and describe briefly the details used. NOTES
METHOD I . MODIFIED ALLEN AND BISHOP METHOD-~ranSfer
0.5495 g. to a tall form beaker, 300 to 400 cc. capacity, and add 6 to 8 cc. of a mixture of 2 parts by volume of liquid bromine
Vol.
a blank test to determine and correct for any sulfur present in the reagents used. The bromine and carbon tetrachloride should be tested before using, as some lots of these reagents marked C. P. have been found to contain considerable amounts of sulfur compounds. Baker and Adamson’s make of these reagents, marked pure, and specified to be free from sulfur compounds, have been found satisfactory. 2-F0r, packing Gooch crucibles, long fibered Italian asbestos (if obtainable) which has been prepared by scraping up into lint and digesting with strong hydrochloric acid to remove impurities, is especially recommended. 3-The method of Allen and Bishop as originally presented by the authors may be found among the original communications, Eighth International Congress of Applied Chemistry, Vol. I, PP. 33 to SI. 4-When igniting the barium sulfate it is advisable to observe the precaution proposed by Folin.’ To avoid mechanical loss the crucible should be provided with a cover and bottom. If a porcelain Gooch crucible is used the cover for a platinum crucible may serve as a bottom, the crucible resting on the platinum lid which is supported by a triangle. The flame is applied to the platinum lid. Folin states that unless this precaution is observed, mechanical loss of barium sulfate follows. I-Run
REMARKS
I-Please supplement your report with any comments you care to make. 2-When reporting results please give individual results as well as averages and in order that there may be no misunderstanding report moisture, sulfur (wet basis), and sulfur (dry basis). 3-Please state whether or not you have had previous lexperience with the Allen and Bishop method, either as originally proposed or as slightly modified under Method I above. Also state if you have found any difficulties or objectionable features 1J
. Biol. Chem., 1 (1906). 149.
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
47
TABLE I-PYRITE CHECK SAMPLE NO. 4 PER CENT SULFUR ON DRY BASIS Orig. Mod. , Misc. Mod. Mod. ANALYST HzO Mod. Misc. h.lpd. Mod. Orig. Hz0 Misc. No. Per cent A. and B. A. and B. Lunge A. and B. A. and B. Misc. Per cent A. and B. A. andB. Lunge 41.92 34.. 0.21 41.31 41.28 1 0.02 41.92 0.24 42: i 4 35 . ... 41.09 41.42 2 0.14 41.96 0.16 36.. ... 41.30 4i:i7(0) 41.44 3 0.23 41.96 0.25 41.54 37.. 4i:j9(b) 41.49 4 . . . . ... 0.24 41.98 0.12 38. 4i :go 41.51 5 0.22 4i:i5(c) 4i 149 41.99 39. ...... 0.12 ... 41.51 4i:;o 6. 0.19 41.17 41.99 40. 41.53 7... 0:io 42.03 0.13 41.. ... 40.06(m) 9 (s) 4i:k 1:: 41.54 8 0.21 41 .02 (n) 4i:i2(d) 41.55 9 42.09 42.15 42.. ..... 0.07 ... 4i:k3 1:: 41.60 IO o:i7 0.18 42.31 43. ... 42.18 4i:ki(e) 41.66 11 0.21 42.36 41.95 44. 0.08 41.94(f) 42.39 45. 0.21 4Ot9O(g) 9 (s) 41.68 12 0.16 0.11 42.50 46. 40196 ( f i ) 41.40(h) 0.17 47. 41.68 13 0.18 0.03 4 i : i i 48.. 41.68 4i:h 14 0.18 49 0.25 41.25fr) 41.69 15 0.21 50 0.12 4i:ii 41.70 4 i :k5 16 0.27 51 0.10 4i:ji ... 41.71 0.17 17 AVERAGE,0.16 41.71 ... 18 0.21 ... 41.71 4i : i 4 19 0.13 SUMMARY OF RESULTSOBTAINED BY 51 ANALYSTS IN 39 LABORATORIES 41.72 20 0.23 4i:51 41.73 21 0.16 Method of Allen and Bishop Misc. Modifications of Misc. 4 i ' i 9 ( ~ 41.73 22 0.21 Analysis Mod. Orig. A. and B. Lunge Methods 41; 99(i{ No. analysts 46 19 4 12 9 41.74 23 0.17 No. laboratories.. 36 15 3 10 8 41.76 24 0.17 42.18 Maximum 42.50 41.94 42.14 42.34 41.77 25 0.22 41.09 Minimum 41.28 41.25 40.96 41.35 4i:j4 41.79 26 0.12 Average 41.80 41.70 41.53 41.44 41.89 4i:j4 ... 41.81 27 0.02 41.78 41.81 28 0.13 It is interesting t o note that of the 46 results reported by the modified 41.69 41.83 29 0.10 Allen and Bishop method: 41.86 30 0.12 36 are between 41.50 and 42.00 incl. and average 41.82 41.86 31 0.16 22 are between 41.60 and 41.90 incl. and average 41.74 41.92 32 0.10 19 are between 41.65 and 41.85 incl. and average 41.73 41.92 33 0.12
ANALYST No.
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T h e results received from t h e thirty-nine (39) laboratories appear in Table I. It is somewhat disappointing t h a t t h e discrepancy between t h e maximum and minimum results by t h e modified Allen and Bishop method is so great, b u t as noted in t h e S u m m a r y of Table I, by omitting t h e extreme results, the agreement becomes very good indeed, a n d t h e average remains practically t h e same. It m a y be further stated t h a t t h e results of those analysts who are thoroughly familiar with t h e original or t h e modified Allen a n d Bishop method are in very close agreement. T h e variation from t h e average by t h e modified Allen a n d Bishop method was, with b u t very few exceptions, not t o exceed, plus or minus, 0 . 2 5 per cent. sulfur. While t h e maximum discrepancy b y t h e Lunge method is not so great a s by the modified
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in this method and how you regard i t as compared t o other methods. 4-Considerable time and work are required to properly arrange and classify a large number of results for easy reference and you are urgently requested t o make your report by August I or as soon thereafter as possible.
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(a) Practically same as modified A. and B. except C C t omitted and precipitation done in smaller volume. (b) Nitro-hydrochloric acid together with bromine and CClr used t o effect solution and then analvsis comuleted by - Lunge - method. (c No details of method given. (d]0.458 g. in 250 cc. copper assay flask with 10 cc. HzO 10 cc. CCla, 15 cc. ench HCl and "Os saturated with bromine and all a t 40' and let stand a t room temperature for 15 min. Heat very gradually and evaporate t o 5 CC. Add 5 cc. HC1 and 5 g. "4'21 and heat until bubbling ceases. Add 5 CC. HCI, 25 cc. HzO, boil, filter, dilute t o 200 cc., and to this solution heated t o boiling, add slowly 25 cc. of a boiling solution of I O per cent barium chloride and 150 cc. HzO. Boil 5 min., settle 45 min in warm place, filter, etc., Wt. X 30 = per cent S. (e) 0.5495 g. dissolved in 30 cc. HNOa, 10 cc. HCl, and 0.2 t o 0.3.g. KClOa in 325 cc. Kje!dahl.flask. Room temperature a t first, finally increasing heat until residue 1s paste, add 10 cc. HCl and evaporate as before, repeat twice. Add 2 cc. HCI and 50 cc. water, reduce with aluminum powder, and finish as by modified A. and B. Same as (e) except using Ir;aBrOs instead of RClOs. Solution by Lunge method using "03 and HCl. Solution by A. and R. method, completing analysis by Lunge method. Average of results by (g) modifications of combined A. and B. and regular method. 0')0 5 g. in No. 3 beaker, add few drops HnOand 1 g. KClOa, and mix. Add 20 cc. "01, cover and let stand cold 20 min., then add 20 cc. nitric chlorate mixture and place on steam plate and heat until solution is complete. Rinse down cover and sides of beaker and evaporate t o dryness. Evaporate twice more with HCl. Add 25 cc. 1 : 3 HCl and heat for 40
ATLANTA, GA., June 1917
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min. Filter and make ammoniacal while hot but do not heal. Have volume 300 cc. and add excess BaClz solution. Add HCI t o dissolve iron precipitate and stir thoroughly, but do not boil. Let stand over night, filter etc. (d) 0.2727 g. dissolved in 250 cc. beaker about same as in ( j ) and after evaporation take up in 12 cc. HCI and heat until foaming ceases, Then dilute until beaker is abouts',2 full, heat and precipitate with 25 cc. hot Boil few minutes and filter after 1/2 hr 10 BaClz solution 0.625 L. in 256 cc. flask. '/e t o 1 cc. bromine added. 1.9 cc. "On and
%
boil few minutes and let stand 3 t o 5 hrs. or over night filter, etc. { m ) Modified Lunge method solution in HNOs and'HCI. n) Same as (nz) except bromine added with "Os and HCI. o j Same as 0 ) excepi used 0.5 g. sample. OI Same as f m ) exceot made solution in "On. . HCI.. and RClOs. No descriptibn gi;en of method used. r) Sample dissolved in 1/z g. KClOs and 10 cc. "Os saturated with KClOa, cover beaker, and quickly bring t o boil. Evaporate finally a t low heat. Evaporate again with 10 cc. HCl. Take u p with 2 cc. HCl and 60 t o 75 cc. Hz0, and reduce iron with granular aluminum. Filter and dilute t o 300 cc., add 5 cc. HCl, boil and precipitate hot with 10 per cent BaClz solution, added slowly and with stirring. Let settle 11/%hrs., filter, etc. (s) Omitted from average.
Allen and Bishop method, yet t h e agreement b y t h e latter method, with few exceptions, is much closer. It seems t o be true in this case, as in most others which t h e writer has observed, t h a t in t h e analysis of check samples, when the same method or apparently tEe same details of analysis are employed, elimination of a few of the extreme results does not affect t h e average. T h e reasons for t h e discrepancies by t h e original or modified Allen and Bishop method have not been apparent. Except in a few cases, t h e observance of t h e following recommendations will probably eliminate most of these: I-In the oxidation and solution of t h e sample t h e initial reaction should not be allowed t o proceed too rapidly and sufficient time should be allowed t o elapse after adding t h e bromine and carbon tetrachloride mixture. Several have recommended t h a t t h e time of standing be inkreased from I j t o 30 min. I t has also been shown t h h t evaporation a t too high temperature a n d allowing t h e beaker t o remain on t h e hot plate at this high temperature causes loss of free sulfuric acid. 2-Carbon detrachloride and some lots of bromine often contain some sulfur compounds, causing high blanks which are undesirable. Several have recom-
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
48
mended t h a t glacial acetic acid be substituted for carbon tetrachloride as a carrier for the bromine, as this can be obtaiged absolutely free from sulfur more generally t h a n carbon tetrachloride. 3-Care should be taken in t h e ignition of t h e barium sulfate in Gooch crucibles. One laboratory reported a long series of results showing the effect of different periods of heating, indicating clearly t h a t barium sula fate underwent decomposition. This is probably true only in rare cases. Some laboratories observe t h e precaution, after the ignition of t h e barium sulfate, of adding a drop or two of strong sulfuric acid and again igniting. One laboratory reported a long series of results, showing a continued loss in weight following several periods of ignition. Folinl refers t o this and recommends t h a t when Gooch crucibles are used, they be protected from direct action of the flame by setting t h e crucible on a platinum lid or some similar arrangement. Ignition in this manner and over a direct flame have yielded the same results in our laboratory. It seems likely t h a t t h e error in personal manipulation is t h e cause of some of t h e discrepancies in the extreme results, though just how, or a t what stage in t h e analytical procedure, is not known. I n this laboratory uniform results have always been obtained both b y t h e original and modified Allen and Bishop methods, t h e latter being preferred. T h e figures in Table I1 illustrate this uniformity. TABLE 11-RESULTS OBTAINED ON PYRITE SAMPLE N O . 4 I N LABORATORY OF
ARMOUR FERTILIZER WORKS,ATLANTA, BY THE MODIFIEDALLEN AND BISHOP METHOD H20 Sulfur (DB) B v whom analvzed. etc.1 Per cent Per cent Analyst “A”. 0.21 41.69 Thoroughly familiar with method. 41.68 41 6 5 1 41:68 AV.41.69 41 681 41:74) Analyst “B”. 0.18 41.72 Man who makes most of the sulfur de41.71 41.67 Av.41.68 terminations. 41.67 41.63 Analyst “C” 0.21 41.68 Had made previously a few determinations by this method 41.75 Analyst “D”. 0.17 41.68 A new man who had never seen or used the ; :1 )Av. 41.77 method before but who had used the Lunge method ........................ 41.76 0.17 41.67 Analyst “E”. A colored helper who has only once before 41.78 made a determination by this method. 4 1 , 8 1 Av. 41.74 He is a careful worker and able t o follow instructions intelligently.. 41.68 1 Each man selected a separate sealed bottle of sample, worked a t different times and entirely independently, and followed strictly the details given. The individual results reported above include all t h a t were obtained. No single result was omitted. The maximum difference between 22 results on 5 separate samples by 5 analyses is 0.18 per cent and the maximum difference between results on 3 samples by 3 men who had had previous experience with the method is 0.12 per cent.
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It would be interesting t o know at which step or steps in the analytical procedure errors are most likely t o creep into t h e work, so t h a t t h e necessary precautions could be pointed out generally and applied. T h e writer’s rather extensive experience with t h e method has failed t o disclose sources other t h a n those included i n t h e three mentioned above. I n order t o discover, if possible, other causes and a t just what stage or stages these errors occur, t h e following plan was proposed in a r e p x t sent out several months ago t o all collaborators : 1
J . Biol. Chem., 1 (1906), 273.
VOI.
11,
N ~ I.
That a sample of sulfuric acid, approximately half normal, or of such strength that 5 0 cc. would equal z g. of barium sulfate, be sent out and that the following tests on this solution be made: A-Titrate 50 cc. against pure sodium carbonate, and against any other standard solutions you may have. B-Precipitate 5 0 cc. after dilution directly with barium chloride solution, cold, as by the Allen and Bishop method. C-Add to 5 0 cc. of the solution ferric chloride about equal to the iron equivalent of pyrite, evaporate to dryness, and finish as by the modified Allen and Bishop method. D-Add to 50 cc. of the solution ferric chloride as above, reduce directly with aluminum powder, and finish as by the modified Allen and Bishop method. Results b y t h e above procedure would check up t h e method in all of t h e important stages and should serve t o help t o point out a t what stage in t h e analytical operation most of t h e errors creep in. There are some objections t o this scheme, for example, the errors in measuring exact portions, b u t with a carefully calibrated pipette t h e errors for measuring would be so small as compared t o t h e errors in results on pyrite samples t h a t this objection would not be so important. T h e accuracy of t h e measured portions could be confirmed by weighing. T h e response t o this proposal was not very general, owing t o present conditions and pressure of regular work. Such a plan of cooperative work would check up t h e analytical scheme in its various stages and should, i t seems, show‘each analyst the main cause of his discrepancies. If t h e interest seems sufficient t o warrant t h e effort, this plan may be proposed again a t a later date. TABLE111-SUMMARY
OF RESULTSFROM 15 OF THE 17 COLLABORATOR-
1915
Miscellaneous Modifications A and B Method and Lunge Method Sample Sample Sample Sample No. 15095 No. 15096 No. 15095 No. 15096 Number of analyses 6 6 18 17 Max. per cent sulfurl.. .... 39.59 47.87 40.00 47.88 Min. per cent sulfur.. ..... 39.15 47.31 38.60 46.60 39.47 47.49 39.18 47.28 Average per cent sulfur. , 1 All results for sulfur are on dry basis. TABLEIV-SUMMARYOF RESULTSREPORTED BY LABORATORIES HITHERTO THOROUGHLY FAMILIAR WITH THE ALLEN AND BISHOP METHOD, EITHERI N ITS ORIGINAL OR MODIFIEDFORM-1916 SAMPLE No. 2 SAMPLE No. 3 Same as No. 15095 Same as No. 15096 in Table 111 in Table I11 SAMPLE No. 1
..
Maximum... 53.27 53.14 53.34 39.82 39.64 39.89 47.33 47.26 47.39 Minimum 52.60 52.71 52.89 39.18 39.13 39.50 46.91 47.17 47.12 Averaze ..... 52.98 52.96 53.11 39.53 39.46 39.63 47.22 47.23 47.28 (a) Method 1 is same as the modified Allen and Bishop method described previously in this paper.
...
TABLEV-METHOD 1, INCLUDING ONLY LABORATORIES FAMILIAR WITH ALLENAND BISHOPMETHODAND OMITTINGTHE MAXIMUM AND MINIMUMRESULTSI N CASE OF EACH SAMPLE-1916 Sample Sample Sample hTo. 2 No. 3 No. 1 Number of analyses 11 10 8 39.66 47.32 Maximum... 53.14 39.42 47.18 Minimum 52.74 39.53 47.24 52.99 Average
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T h e writer feels t h a t t h e main purpose in this cooperative work on t h e determination of sulfur in pyrite has been largely accomplished, namely, t h a t i t has been shown t h a t t h e Lunge method in its various modifications gives results between quite wide limits, and in t h e hands of most analysts, at least, is not t o be com-
J a n . , 1919
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
p a r e d i n accuracy a n d reliability t o t h e original or modified Allen a n d Bishop method. Fur$her, t h a t t h e l a t t e r method is a n excellent one, easy a n d simple of manipulation. M a n y laboratories hitherto unfamiliar with this method have now adopted i t , either i n its original or modified form, with t h e result t h a t in future better agreement among laboratories on this determination may be expected. Tables 111, IV, a n d V give a brief summary of t h e work for t h e two previous years. It will be noted in Table V, comparing results of Samples z a n d 3 with results on t h e same samples for t h e previous year, t h a t t h e results on Sample 2 for both years are in close agreement, b u t in case of Sample 3 , results are considerably lower t h a n those i n 1915. T h e reason for this is t h a t Sample 3 is a sample of Spanish ore, which oxidizes quite rapidly when finely ground, a n d when samples for 1916 were bottled u p after remixing t h e large portion, a distinct odor of SOz was observed. CONCLUSIONS
T h e conclusions arrived a t for t h e work of previous years seem t o apply equally t o t h a t of t h e prehent y e a r a n d a r e as follows: I-The disagreement b y t h e Lunge method is about i n line with past experience. z-The agreement b y t h e Allen a n d Bishop method, e i t h e r t h e original or t h e modified, is much better a n d in t h e hands of analysts experiehced with t h e method yields results in close agreement, closer, in fact, t h a n is t h e case with most analytical determinations. 3-The Allen a n d Bishop method is recommended t o all chemists as a n accurate method for determinat i o n of sulfur in pyrite. T h e writer wishes t o t h a n k again all those who have so generously participated in this undertaking for their work a n d valuable suggestions. It is hoped t h a t all who have t a k e n p a r t feel amply repaid for their efforts a n d it is believed t h a t i n future a better agreement between laboratories for t h e determination of sulfur will be observed.
49
F r o m these tests t h e offset sample would appear a good match in strength t o t h e rope stock. B u t envelopes made from t h e offset stock proved worthless. An off-hand examination of these two papers with t h e fingers showed a great difference in t h e tearing quality as is t o be expected when t h e difference between their compositions is considered. A Schopper folding tester would, no doubt, have shown a great difference between these papers, b u t none was at hand. A means was t h e n sought for measuring t h e tearing quality of paper. T h e method finally adopted gave t h e following results on t h e two samples mentioned: TEARING RESISTANCE
............................... ............................
With grain Across grain..
Rope Stock Grams 240 250
Offset Stock Grams 95 125
T h e test as now used has many disadvantages, b u t gives reliable information, particularly when used along with t h e Mullen tester. A low Mullen test a n d a high tearing resistance is sometimes a highly desirable condition. T h e Mullen tester shows t h e hardness a n d rigidity, while t h e tearing resistance shows t h e fiber strength a n d t h e extent of peeling. A wrapping paper t h a t peels when tearing is certainly superior t o one t h a t does not. T h e effect of humidity variation upon t h e results obtained with t h e tearing-resistance tester has not yet been worked out. T h e indications are t h a t these tests are not affected t o t h e same extent as those made on t h e Schopper folding tester. T h e details of making t h e test are as follows: Twelve strips, I in. b y z1/2 in., are cut from samples representative of t h e lot t o be tested. Six of t h e m are cut with t h e long dimension parallel t o t h e grain of t h e paper, a n d six are cut across t h e grain. These are c u t with t h e scissors, as shown in Fig I . It is easier t o slit t h e t e s t piece t o about in. from t h e end of t h e strip a n d t h e n t o cut off t h e end AA‘, so t h a t t h e slit stops in. from t h e end. A knife slit is not t o be recommended; neither should t h e t i p of t h e scissors be used a t t h e end of t h e slit.
ARMOUR FERTILIZER WORKS GEORQIA ATLANTA,
A‘
A PAPER TEARING-RESISTANCE TESTER By H. N. CASE Received August 9, 1918
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T o anyone making a review of t h e literature on s t r e n g t h tests for paper, t h e subject would appear simple a n d quite well defined. After making tests on t h e Mullen “pop tester” a n d the Schopper tensile machine, t h e writer was therefore surprised t o find t h a t t h e results often bore no relation to the usefulness of t h e paper. For example, t w o papers were t o be compared for use in making “tension envelopes.” T h e one was a rope Manila a n d t h e other a short fibered offset paper. These results were obtained : Weight per ream, 500 - 24 X 35 inches.. Mullen test ............................. Tensile strength on Schopper tester With grain.. ....................... Across grain..
......................
.
..
Rope Stock Lbs. 79
54 Kg. 12.6 6.5
Offset Stock Lbs. 79
sa
Kg. 14.0 7.0
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A FIG.1
T h e apparatus (Fig. 2 ) is provided with a set of three buckets of different sizes, so t h a t when filled with water a range of weight from 1 5 t o 600 g. can be obtained. One of these buckets is selected according t o t h e strength of t h e paper. T h e test piece is clamped, as shown, a n d t h e water allowed t o r u n slowly into t h e bucket until t h e two parts of t h e piece completely separate. T h e cock i s
