March 15, 1935
ANALYTICAL EDITION
producers, however, might find it worth while to put their sampling on a sound basis in this way. Under some conditions it is possible to estimate from sampling records what the actual over-all error in sampling, reduction, and analysis has been. Thus, suppose that we have two or more check samplings on successive lots of coal from the same plant; if the actual variability of the coal corresponds to a standard deviation 6 and the sampling errors of the two series correspond to standard deviations €1 and €2, respectively, the ash values in the separate series should show standard deviations d62 el2 and 1 / 6 2 eZ2, and the differences between the two samples on the same lot should show a standard deviation d e l 2 eZ2. These three relations permit the determination of 6, el, and e2. This has been done in a number of cases. Figure 2 shows a typical result. .
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In this case 88 cargoes of 1000 to 1400 tons of nut and slack through a 2.125-inch bar screen were sampled by producer B and by consumer I . The B samples were taken by increments of 1.5 pounds as the nut and slack coal flowed into the car, an increment being taken every time a mine car (1-ton capacity) was dumped. The gross samples, which always weighed more than 1500 pounds, were crushed and reduced by hand; a 3-pound can was sent to the laboratory. The consumer took a 500-pound gross sample by automatic machinery; this was crushed mechanically, reduced, crushed to 10-mesh, reduced again, and crushed again to 60-mesh t o give the I samples. Standard methods of analysis were used in both cases. In Figure 2 the 88 cargoes have been numbered in the order of increasing ash as found by B, and the results of both B and I then plotted against
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the cargo number. The two corresponding analyses appear at the two ends of a line, that made by Z being marked with a circle. It is obvious from a glance at Figure 2 that there is almost no connection between the results found by B and Z for identical lots of coal. Calculation shows that the B samples have a standard deviation of 0.37 er cent and the I samples of 0.55 per cent, while the true ash in &e cargoes has a standard deviation of only 0.18 per cent. Reference to tables of the probability integral then shows that while the I samples are in error by a t least 1 per cent seven times in 100 and the B samples seven times in 1000, a cargo of coal will differ by 1per cent from its average value less often than once in 10 million times. This last result is misleading, as the distribution is certainly not Gaussian at the extreme ends, and many contingencies which were absent for 88 consecutive cargoes might occur once in several thousand times with a resultant large effect on the ash. Nevertheless, the chances are excellent that any particular abnormal ash value does represent a sampling error.
LITERATURE CITED (1) Bailey, J. IND.ENQ.CHEM.,1, 161 (1909). (2) Findlay, Power Engr., 29, 47 (1934). (3) Grumell and Dunningham, British Engineering Standards Assoc., No. 403 (1930). RECEIVED August 30, 1934. Presented before the Division of Gas and Fuel Chemistry a t the 88th Meeting of the American Chemical Society, Cleveland, Ohio, September 10 to 14, 1934. Published by permission of the Director, U. S. Bureau of Mines. (Not subject to copyright.)
Viscosity Data for Commercial Rosin and Abietic Acid GEORGE S. PARKS, MONROEE. SPAGHT,AND LOISE. BARTON Department of Chemistry, Stanford University, Calif. HE viscosities of some amorphous samples of commer- tures for a day or more. Its acid number was 161. The cia1 wood rosin and abietic acid have been measured commercial abietic acid was light yellow in color and had an in absolute units within the temperature range - 28" to acid number of 170.5. The viscosity m e a s u r e m e n t s 135' C. Theae measurements, above 80" C. were made by the fallwhile they were made primarily I 1 1 ing-sphere method. For the use of as a part of an extensive investi1 1 this method the densities of the gation of liquids that form glasses ,~ I three substances were required and or amorphous solids on cooling, accordingly these were measured a t Dossess considerable technical interest in themselves; hence, the Y 3 loo", 130°,and 160" C. witha Pyrex specific gravity bottle. The resultresults will be briefly summarized ing values conformed closely to the here. I n a sense they serve to sup- * linear equations : plement the earlier study by Peter- ' son and Pragoff (3) on the viscosity Rosin FF, d = 1.094 - 0.0006 t of rosins, which covered the temRosin I, d = 1.075 - 0.0006 t perature range 125' to 200' C. Abietic acid, d = 1.077 - 0.0006 t The samples of commercial wood where t refers to the Centigrade rosin and abietic acid investigated temperature. The viscosity measwere kindly supplied by the Herurements below 80 O were made with cules Powder Company. The rosin , a concentric cylinder viscometer. was of two grades-FF and I. The *" Full details concerning the apparaformer was a dark brown material, ,: tus and procedure with each method which showed no tendency to crystallize. Analyses in the authors' i FIGURE1. LOGARITHM OF VISCOSITY PLOTTED have been given by Parks, Barton, Spaght, and Richardson (9) in their laboratory yielded about 155 for its AGAINST TEMPERATURE work on undercooled liquid glucose. acid number. Rosin I was a puriA commercial abietic acid. E wood rosin I: C. wood rosid FF. In t,he case of abigtic bcid the circles represent Temperature measurements, which fied, reddish amber material, which individual valuee obtained in the present study, the heayy dots represent two or more values which practically coingenerally represent one of the limitfrequently crystallized when kept cide and the crosses show the results of Bingham and ing factors in accurate viscosity at moderately elevated tempera-. Stedhens.
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INDUSTRIAL AND ENGINEERING
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determinations, were made with thermometers calibrated by the U. S. Bureau of Standards and readable to * 0.02'. In the course of the investigation forty-eight individual viscosity values were obtained with seven different samples of the abietic acid, forty-eight viscosity values with six separate rosin I samples, and thirty-one viscosity values with four rosin FF samples. In general, a series of values obtained with any one sample was found to lie very consistently on a smooth curve and to be highly reproducible, but apparently the various series with different samples of the two rosins and abietic acid could differ appreciably. This behavior is, perhaps, not surprising in view of the fact that the materials were commercial products and that viscosity is a property of matter which is often extremely sensitive to small differences in the composition and even in the preparation (thermal history) of the samples. Figure 1, in which the common logarithm of the viscosity (in poises) has been plotted against the Centigrade temperature, shows all the viscosity results in the case of abietic acid. The smooth curve A appears to be fairly representative of these data, indicated by the circles and dots, which have been obtained in the present study. The crosses, lying somewhat below this curve, are the values for abietic acid recently published by Bingham and Stephens (1) as representative of the results found with their alternating stress method. In all cases the authors' results indicated true viscosity and not plasticity; and this was also the conclusion of Bingham and Stephens, who measured a viscosity as large as 7.2 X 10" poises at 20" C. Curves B and C serve to show how results for rosin I and rosin FF compare with those for the abietic acid. To avoid confusion in the figure the individual points for these data have been omitted. It is interesting that the darker, or cruder, rosin has an appreciably higher viscosity than the commercial abietic acid, while rosin I is consistently lower
CHEMISTRY
Vol. 7, No. 2
within the temperature range of this study. At the upper temperatures the authors' rosin curves overlap to some extent the viscosity determinations published by Peterson and Pragoff (8) and in this region the two investigations are in fair agreement. Thus for rosin I, Peterson and Pragoff found a viscosity value of 2.83 poises a t 125' C., while curve B in the authors' study corresponds to 2.5 poises. In the case of rosin FF the earlier investigators found viscosities of 5.95 poises a t 120" C. and 2.56 poises a t 130" C.; and the present study yields 7.4 and 3.3 poises, respectively, a t these two temperatures. TABLE I. VISCOSITYDATAFOR WOOD ROSINAND ABIETICACID TEMP.
ROSINFF Log100
ROSINI Log100
ABIETICACID Logloll
28 30 40 50 60 70 80 90 100 110 I20 130
10:?3 9.00 7.38 5.96 4.69 3.62 2.70 1.93 1.34 0.87 0.52
10.06 9.73 8.11 6.60 5.23 4.04 3.06 2.23 1.54 0.98 0.57 0.27
10.68 10.35 8.71 7.07 5.68 4.40 3.33 2.43 1.78 1.10 0.65 0.31
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In Table I are given a series of "best values" for viscosity results with these three materials, obtained by reading off the logtoq values corresponding to even temperatures in an enlargement of Figure 1. For convenience in tabulation the data have been kept in the form of the common logarithm of the viscosity (in poises). LITERATURE CITED (1) Bingham and Stephens, Phusics, 5,217 (1934). (2) Parks, Barton, Spaght, and Richardson, Ibid., 5, 193 (1934). (3) Peterson and Pragoff, IKD. ENQ.CHEM.,24, 173 (1932). RECEIVED January 14, 1935
A Rapid Method of Preparing Biological M.aterials for Phosphorus Determinations H. W. GERRITZ, Agricultural Experiment Station, S t a t e College of Washington, Pullman, Wash. IFFICULTY has been encountered in preparing cattle cubic centimeters of cattle urine are thus digested in 15 minutes and sheep urine for total phosphorus determinations. and 2 grams of feed require about the same time. PhosThe low phosphorus content requires the digestion of phorus determinations on perchloric acid-digested samples large quantities of urine and the removal of the organic matter have been found to be accurate and to compare well with requires vigorous oxidation. In digesting with nitric and determinations by official methods (1). hydrochloric acid, it is practically impossible to obtain a clear Very good recovery of added phosphorus has been made. solution. Sulfuric-nitric acid digestion with further addition Table I shows the accuracy with which phosphorus may be recovered from s t a n d a r d of nitric acid or sodium nis o l u t i o n s gravimetrically, trate requires 2 hours' divolumetrically, 01colorimetgestion or more to clarify TABLE1. RECOVERY OF pHosPHoRUs AFTER PERCHLORIC ACID urine samples. The same DIGESTION OF STANDARD SOLUTIOXS rically, after perchloric acid (Phoaphorus added a6 K2HPOd digestion. Standard solumethod of digesting feeds VOLUM~TRIC COLORIMETRIC t i o n s of potassium phosand feces requires 1 to 2 GRAVIMETRIO METHOD METHOD METHOD phate were placed in Kjelhours. Recovered Recovered Recovered dah1 flasks and filter paper The use of perchloric acid after after after in with nitric Phos horue €IC104 Phos horus HClOa Phos horus HClOi afded digestion a&ed digestion acfded digestlon was added to Organic and sulfuric acids or with Gram Gram Gram Gram Gram Gram matter. The organic matter 0.0060 0 0060 0 0017 0.0018 0.0057 0 0057 was removed by oxidation sulfuric acid alone has been 0 0019 0 0057 0 0058 with sulfuric, nitric, and perfound to accelerate the clari0 0058 0.0017 0.0057 0 0058 0.0019 0.0057 chloric acids, as in determif i c a t i o n a pp,r ecia b l y 0.0058 0.0018 0.0057 through r a p i d , vigorous 0.0060 0.0018 0.0057 nations of phosphorus on oxidation. T w e n t y - f i v e biological materials.
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