7d
Vol. 3, No. E
ANALYTICAL EDITION
a mixture of 4 parts of phenol, 2 parts of 0-cresol, 1 part of m-cresol, and 1 part of p-cresol. The effect of variation in temperature is shown in Table 111, the weight taken in each case being 0.025 gram. There remains the error due to calculation of both cresols and phenol in terms of phenol. This may be eliminated if de-
(3) Ditz and Cedivoda, 2. anal. Chem., 38, 873 (1899). (4) Kolthoff and Furman, “Practical Volumetric Analysis,” Vol. 11, p. 475, Wiley, 1929. ( 5 ) Koppeschaar, z, anal. Chem, 16, 233 (1876). (6) Lloyd, J , Am. Chem. sot,, (1g05). (7) Messenger and Vortmann, Bey., 23,2753 (1890). (8) Pence, J. IND. ENQ.CHEM.,4, 518 (1912).
Literature Cited
(13) Williams, I N D . ENO. CHEM.,19, 630 (1927). (14) U. S. Steel Corporation, “Sampling and Analysis of Coal, Coke, and By-Products,” p. 153, Carnegie Steel Co., 1929.
(1) Autenrieth and Beuttel, Arch. Pharm., 248, 112 (1910). (2) Chapin, U.S. Dept. Agr., Bull. 1308, 17 (1924).
Should a Change Be Made in Analytical Procedure for Evaluating Available Phosphoric Acid Content of Fertilizer Materials?‘ C. C. Howes and C. B. Jacobs DAVISOK CHEMICAL CO.,BALTIMORE, MD.
phate had been formed to be soluble in the 100 cc. of neutral ammonium citrate solution. With this deviation the insoluble P205 present was changed entirely as will be noted in Table I. Table 11-Elf e c t on Insoluble PzOa Results by Varying pH Value of A m m o n i u m Citrate Solution AMMONIUM CITRATE SOLN.
INSOLUBLE Pa06 Ammoniated superphosphate
Superphosphate (not ammoniated,
%
%
0.97 0.98 1.00 0.98 1.06 1.16 1.26
0.62 0.62 0.60 0.63 0.62 0.60 0.61 0.62 0.62 0.63 0.61
1.54
2.94 4.23 4.67 6.34 8.12 8.60
0.62 0.69
0.71
WITH I-GRAM PORTION
IUSOLUBLE PzO,
INSOLUBLE PzO, 2-gram sample
% 4 67
2-gram sample
ii~g
I
%
/
% I 2.46 2.12 3.08 5.09 3.97 1.42 1.72
0 94 1.78
1.16
1 02 0 86 0 98 3 42 3 84
I
1
1.60
I
1-gram sample
% 0.44 1.08 1.36 3 20 1.78 0.46 0.62
--- I
This method has been in use with little change for many years and it was with hesitancy, even after thorough painstaking analyses, that these variations were reported. The first of these irregularities was observed when we departed from the official procedure by using a 1-gram portion instead of 2. This deviation was made because it was a t first thought that on the addition of ammonia too much dicalcium phos1 Received September 22, 1930. Presented as a part of the Symposium on “Action of Ammonium Citrate on Superphosphates,”.before the Division of Fertilizer Chemistry at the 80th Meeeting of the American Chemical Society, Cincinnati, Ohio, September 8 to 12, 1930.
7.0
2.30
0.60
After making a number of insoluble determinations on different samples containing varying amounts of ammonia, it became necessary to make up a new neutral ammonium citrate solution. The citrate solution was made up following the prescribed official procedure, using phenol red as the indicator. Following the preparation of the new batch of citrate solution several samples were run that had previously been run with the old citrate solution. The results of these differed very widely from those obtained with the old solution. With these variations it was believed that the difficulty lay in the citrate solution. Upon determining the true reaction of the first citrate solution it was found to have a pH value of 6.5, while the new citrate solution prepared last had a pH value of 7.0. This led to the belief that a slight variation in the pH value of the citrate solution may cause wide variations in the insoluble PPOs results, in material to which ammonia has been added. A number of citrate solutions were then made up with pH values ranging from 4.5 to 8.8. Samples to which ammonia had been added to the extent of 5.76 per cent were then analyzed with
INDUXTRIAL AND ENGINEERING CHEMISTRY
January 15, 1931
each of these citrate solutions. Table I1 shows the results of this experiment. I n addition to these figures a 1-gram portion was analyzed with the citrate solution having a pH value of 7.0. An insoluble Pzo5 figure of 2.3 was obtained, while it will be noted that the 2-gram portion gave an insoluble PzO5 of 4.67 per cent. An experiment similar to that shown in the previous tabulation was made with a normal superphosphate-that is, one to which no ammonia had been added. The results of this experiment are also shown in this table. It will be noted that the variations obtained with the normal superphosphate are within the limits of experimental error. Another experiment to study the effect of varying the ratio of sample to citrate solution was then carried out, in a 65" C. bath for 30 minutes, on a 2-gram sample of normal superphosphate and on one which had been ammoniated 6.2 per cent. An ammonium citrate solution having a pH value of 7.0 was used. Table I11 gives the results of this experiment. Table 111-Effect
on Insoluble PzOn Results by Varying Amount of Citrate Solution
-
AMMONIUM CITRATE
SUPERPHOSPHATE
100 cc.
Not ammoniated Ammoniated
200 cc.
250 cc.
300 cc.
350 cc.
400 cc.
%
%
%
%
%
%
0 83 1 90 5 46
0 78 1 82 2 54
0 74 1 80 2 01
0 69 1 82 1 64
0 66 1 76 1.80
0 64 1 76 149
It will be noted from these results that extreme variations are obtained with ammoniated goods, while the variations with a normal superphosphate are much less and scarcely more than that due to experimental error. Another series of analyses was made to study the effect of the time of exposure of sample to citrate solution, on both the normal superphosphate and ammoniated superphosphate. I n this series both a 1-gram portion and a 2gram portion of sample were used. These results are shown in Table IV. Table IV-Effect
on Insoluble ROj Results by Varying Periods of Digestion Z-GRAM
SUPERPHOSPHATE 1/z
hr.
SAMPLE
1 hr.
l'/z hrs.
I
GRAM SAMPLE '/z hr.
1 hr.
%
%
l ' / z hrs.
a 2-gram portion is again weighed. This means that there is the equivalent of only 1 gram of the ammoniated superphosphate taken in the analysis. Let us for a moment refer back to Table I and the first illustration given. This sample shows, with a 2-gram portion, 4.67 per cent insoluble PzOS, and with a 1-gram portion, 2.30 per cent insoluble Pz06, a difference of 2.37 per cent insoluble phosphoric acid. Such practice could not be tolerated very long. It would mean either reworking the material or sustaining a loss of 2.37 units of phosphoric acid. The same results in varying degrees will be found, depending upon the amount of ammoniated superphosphate used to compose the finished fertilizer mixture. I n addition to plant control difficulties, an unfair discrimination is made against the manufacturer of ammoniated superphosphate in favor of the dry mixer who uses it. The present official method specifies that the ammonium citrate solution shall be neutral, but further states that phenol red may be used as the indicator to determine the neutral point. This leaves it optional with the analyst where no standard indicator solutions are available, as to what the neutral point with phenol red may be, His choice of the neutral point may be anywhere between 6.8 and 8.4, although one would not expect extreme variations. As a matter of curiosity, samples of supposedly neutral ammonium citrate were obtained from a number of laboratories engaged in fertilizer work. The pH value was determined on each of these solutions and they were found to have a range from 6.1 to 7.1. Referring back to the insoluble determinations shown in Table I1 and visualizing material of this nature being compounded according to the results yielded with the citrate solution having a pH value of 6.1 and later being analyzed in a state control laboratory with a citrate solution having a pH value of 7.0, the results would have a great tendency to place the manufacturer offering such goods in a very bad position. Should it so happen that the pH value of the citrate solutions of the plant control laboratory and the state laboratory be reversed, the results would have a tendency to cause the factory management to make a change in their personnel. However, the results obtained with citrate solutions covering the pH range just mentioned, applied to unammoniated goods, would be satisfactory as shown in Table V.
%
Table V-Variations i n Insoluble PZOSResults with Change i n pH Value of Citrate Solution
lvEIGHTl
Ammoniated
71
CITRATE-IWOLUELE SOLUTION PD, WHEN Is:
p~
OF CITRATE
OF
Difficulties with Qfficial Method
The official method as it now stands seems to serve well in cases where ammonia has not been introduced, but from the data given in the preceding tabulations it is quite evident that this method will not serve without alteration in cases where ammonia has been introduced. Under the present status innumerable difficulties may be expected. For instance, let us picture for a moment conditions where a manufacturing department depends entirely on the laboratory to govern the compounding of its materials. Good practice demands that the laboratory follow the official method as closely as possible. Let us suppose that ammoniated superphosphate is to be used to compose a mixture. The analyst is required to weigh a 2-gram portion. The results of his analysis will be used to calculate the desired amount of the ammoniated superphosphate to be used. Let us suppose further that in compounding this mixture a 16 per cent available P206will be used to give an 8 per cent available PZO5in the finished product. When the sample of the finished material is submitted to the laboratory
' A MPLEI
7.0 6.7 6 . 5 6.2 5.7 5.4 5.0 4.6 4.2 3 . 5 1
%
Gvams
%
%
%
%
%
%
NORMAL SUPERPHOSPHATE-SLIGHT
2 1 2 1
I
0.19 0.18 2.10 2.04
0.18 0.18 2.10 2.18
0.16 0 . 1 6 0.18 0.17 2.11 2.10 2.14 2.08
0.17 0.16 2.06 2.10
0.16 0.20 2.11 2.16
0.17 0.17 2.14 2.14
AMMONIATED SUPERPHOSPHATE-WIDE
%
%
%
-
VARIATION
0.16 0.18 2.15 2.14
0.16 0.16 2.24 2.22
0.16 0.16 2.16 2.12
VARIATION
None None
5.78
2 1 2 1 2 1 2 1 2 1
5.03 5.76 4.76 6 21 ~~~~~
New Method Advocated
The main points a t issue are: First, that the official method for the determination of insoluble Pz06as it now stands is applicable in cases where ammonia has not been introduced,
72
ANALYTICAL EDITION
and the least that can be done is to pay a tribute to the authors who have contributed to such a method that has served well for so many years. We are now confronted with rapidly changing practices and materials, and it is very obvious that it may become necessary to devise an entirely new method to take care of this new product. By continuing with the present method, a hardship is being worked on the manufacturers of fertilizers and on the manufacturers of synthetic and by-product ammonia, as well as on the users of fertilizers. There is no doubt but that the injection of ammonia into fertilizer materials will remedy a number of difficulties with which the manufacturer and farmer have contended for a number of years. By this statement a reduction in the free acid content and an improvement in the storing and drilling qualities of fertilizer materials is meant. By an injection of ammonia as such into superphosphate or superphosphate-bearing fertilizer materials, it is only with the greatest difficulty that the so-called reversion of the available phosphate is prevented. Numerous publications by various investigators lead to the belief that most of the available phosphoric acid under its present classification reverts to an insoluble form shortly after application to the soil.
Vol. 3, No. 1
A number of investigators have also shown that phosphoric acid in that condition is still available as plant food. If these reports be true, and there is every reason to believe that they are, then it seems only reasonable and fair to both the manufacturer and the user that a thorough study be made as promptly as possible of the compounds formed in superphosphate during the injection of ammonia, with a view towards reclassifying and reinterpreting the term "available." Such an investigation involves a large number of pot and field tests and would necessarily have to be accompanied by a large amount of laboratory work. The writers understand that much of this work is now under way. This seems to be one of the most important manufacturing problems with which the fertilizer industry is confronted today. Much benefit will result to all concerned if the maximum amount of this form of nitrogen can be used. It is essential that this question be very definitely worked out and as soon as possible, because the manufacturer must necessarily anticipate his processes of the future. It is a duty of this organization to lay aside all precedent and carry on a well organized system of experiments, the results of which will answer the questions with which we are confronted.
Measurement of Abrasion Resistance I-Paints, Varnishes, and Lacquers' A. E. Schuh and E. W. Kern BELLTELEPHONE LABORATORIES, 463 WEST ST., NEWY O R K , N. Y.
A method of measuring the abrasion resistance of air stream and allowing the INCE organic finishes materials in the form of thin films has been devised. uniform mixture of air and such as paints and varWhile designed primarily for the study of paint, lacCarborundum to i m p i n g e nishes are often subject quer, and varnish films, the method should be useful against a film of known thickto abrading forces, it is desiralso in the study of a wide range of other materials. ness of the m a t e r i a l to be able to evaluate them with reThe method consists essentially in the following: tested. The weight of Carspect to their resistance to Carborundum powder of uniform particle size is adborundum required to wear abrasion. Several m e t h o d s mitted at a constant rate to a directed stream of air through the film is measured have been developed for this under constant pressure and the resulting Carborunand arbitrarily defined as the purpose, some of which have dum-air blast is allowed to impinge upon a film of the abrasion value for a given been described by G a r d n e r test material mounted at a fixed angle. The weight of thickness of the material. (1). Among these, the Parlin Carborundum required to wear through a unit thickObviously, in order to obtain method is representative of a ness of material is taken as the abrasion resistance of reproducibility of measuretype of test in which an abthe material. The development of this test has inment, it becomes necessary to rading surface is moved a t cluded an investigation of the variables pertaining hold the conditions of the c o n t r o l l e d p r e s s u r e and both to the apparatus and to the material under test. test constant. With a view speed over the organic film, to making the method generand the abrasion value taken as the number of passes required to cut through the material. ally applicable, the variables that affectthe abrasion value This method is open to criticism in that an appreciable have been studied both as to their nature and relative magnifrictional heating is produced a t the interface of film and tude. Although the method is by no means restricted to the abrasive and, furthermore, that the abrading surface undergoes variation with use. On the other hand, Gardner's determination of relative abrasion resistance of paint films, falling sand method, in which the abrasive falls by gravity the test has been developed using these as the test materials. through a long confining tube and impinges on the paint It is well known that the properties of material of this type, film, appeared more suitable in principle for the develop- especially when of oleoresinous origin, are much affected by ment of a precise test. The method to be described in the temperature and humidity. It seemed necessary, therefore, present paper has employed a modification of this principle to carry on this study under controlled air conditions. The in that air a t carefully controlled pressure is used to drive effect of temperature and humidity of the air was investigated over a wide range of indoor variation, the air condithe abrasive against the film under test. The present abrasion test consists essentially in admitting tions ranging from 21.1" C. (70" F.) and 41 per cent relative a stream of Carborundum particles into a rapidly flowing humidity to 32.2"C. (90°F.)and 90 per cent relative humidity. The materials tested were: (1) three varnishes of differing 1 Received September 19, 1930. Presented before the Division of oil lengths but of a common synthetic resin; (2) two series Paint and Varnish Chemistry at the 80th Meeting of the American Chemical of lacquers each of a different resin in three different concenSociety, Cincinnati, Ohio, September 8 to 12, 1930.
S
