October, 1923
INDUSTRIAL A N D ENGINEERING CHEMISTRY
1037
Insoluble Phosphoric Acid in Acid Phosphates and Fertilizers' Some Sources of Error in Its Determination By W. R. Austin TENNESSEE CHEMICAL Co.,NASHVILLE, TENN. Per cent I t is important to obseroe the precaution of washing the sample FeaOs article is to emphawith water up to the volume of 250 cc. as prescribed in the oficial ~ ~ ~ ~ ~ , " , ~ ~ ~ " . i i 2*35 b b . ; . ~ After 9-cm. washing filter.. ........... to 150 cc., 2.30 size certain Sources method, and also to select rapidfiltering funnels so that the washing of discrepancies in the determay be done in about 20 to 30 minutes. 11-cm. filter.. .......... 2.30 After washinE t o 200 cc., mination of insoluble PzOS, There is an important relation between the Fez08 and P105re9-cm. filter ............ 2.10 particularly fhose arising moved by thorough washing-as the percentage of FeaOs remowd by Af;?~,Wa;t;.:g, 10. "p". 2. o5 from incomplete prelimiwashing is increased the percentage of insoluble P20s decreases. While the same care should be exercised in making the ammonium Many analysts prefer the na,ry washing of the sample, and the relative effect of 11-cm. filter t o avoid loss citrate exactly neutral, as prescribed by the oficial method, yet moderate dgerences in the ratio of ammonia to citric acid make in washing when churning using various solutions of relatively little difference in the results for insoluble OS compared to up the sample with the ammonium citrate solution. The official met,hod of the importance of careful preliminary washing. stream of water. There the Association of Official is apparently an advanAgricultural Chemists pretage, in the case of some. scribes: "Place 2 grams of the sample on a 9-cm. filter, wash samples, in using a 9-cm. filter, since a greater number of with successive small portions of water, allowing each to washings is required to give the 250 cc. t.han when the 11pass through before adding more, until the filtrate measures cm. filter is used. In most cases, however, ten washings on a about 250 cc. ***." This precaution of washing the sample 11-cm. filter using about 25 cc. each time were sufficient. It has been found with some samples that the percentage of to 250 cc. has not been observed by some analysts, resulting in many cases in wide discrepancies. insoluble afterawashing to 250 cc. is quite appreciably lower I n the case of one sample of acid phosphate made from than when washing to 150 cc. There seems to be an imporTennessee phosphate rock, on which considerable collabo- tant relation between such results and the Fez03-the greater rative anaIytica1 work was done, the importance of thorough the number of washings the more Fez03combined with Pz06 preliminary washing was strongly emphasized. One group is washed through resulting in lower results for insoluble. of analysts, accustomed largely to handling acid phosphate Several samples of acid phosphate were next taken, washed made from Florida rock, reported consistently about 0.75 per to different volumes, and the percentage insoluble P205and cent insoluble PzO6, while others, more familiar with acid Fe203 determined. phosphate made from Tennessee rock, found about 0.40 per -PER CENT INSOLUBLE100 Cc. 150 Cc. 200 Cc. 250 Cc. cent insoluble. After a careful investigation, including Un- (4Wash- (6 Wash- (8 Wash- (10 Washexchange of samples of ammonium citrate, etc., it was develwashed ings) ing.s) ings) ings) Sample C-Acid phosphate I day old (Tennessee rock) oped that the trouble was entirely in the preliminary wash:;, ;&; ;&;;;.: ;:! ;: ;: ing. Those who were in the habit of washing the sample %& at first with only three or four washings with water reported Fe~~n,af'~.Cttrate.I.reat: .. o.40 o.40 o.40 o.25 the highest results. After this investigation further deterSample D-Acid phosphate, 8 months old (Tennessee rock)O minations were made on the same sample, with a close agree- PZOS.. ................. 0 . 3 2 0 . zg a. 20 0.14 0.12 ment averaging, for ten analysts, 0.36 per cent, six of the ~ ~ ~ ~ ' . l o i 2 * 1 0,. '.O09 ~ ~ ~ merit.. .............. 0.43 0.40 0.38 0.35 0.28 llumber reporting 0.37 per cent. This work led to the Sample E-Double superphosphate (45 per cent available P z 0 1 ) ~ following: PzOa ........... .. 2.40 2.25 .. 2.14
T
HE purpose of this
: ,
'c.:
::::
;::;
Sample A-Acid phosphate, after diferenl periods of curing made from Tennessee rock (rock cnnlaining about 2.4 p e r cent AlaOa and 2.7 p e r cent FeaOs) --PER CENT INSOLUBLE PaOsWashed to 100 Cc. Washed t o 250 Cc. Period of Curing (4 t o 5 Washings) (10 Washings) 2.19 1.96 0.94 0.62 1; day 0.48 0.35 4 6 0.49 0.31 0.50 0.38 10 /weelis . 0.65 0.45 12 14 j 0.48 0.33 Sample &Acid phosphate, 6 monlhs old varied size oflilter papers, also volume of water i n washing (prior to tveafment &ith ammonzum cztrate) --PER CENT INSOLUBLE PaOsVolume of Washing CC. 11-Cm.Filter %Cm. Filter - .. 100 0.30 0.27 150 0.25 0.15 200 0.15 0.16 250 0.15 0.15 Sampie tested directly, no preliminary washing with water-0.30 per cent insoluble.
1
Separate portions of Sample B were similarly washed, as above, and the Fez03 remaining in the washed residue determined. 1 Presented before the Division of Fertilizer Chemistry a t the 64th Meeting of the American Chemical Society, Pittsburgh, Pa., September 4 to 8, 1922. .Received August 17, 1923.
in washed residue:: Sample F-Acid
* ' 1'40 *' phosphate, 1 year old (Florida rock) 0.24 0.18 1.20 1.10 phosphate, I week old (Florida rock) 0.55 0.42
1.20
..................... ..
.. ..
0.14
.....................
..
0.38
Pa06 Fez03 in x7ashed residue.. Sample G-Acid Pa06 Sample H Average results for insoluble PzOa on eight samples of mixed fertilizers, containing acid
~. .ff:r.og:n,' ~ . . ~2 . / 3
~
a
tories.
~ .98
~
1,90
~
1.06
~,83
The results in Samples D and E are the average reported hy ten labora-
The importance of thorough washing of the sample with water prior to its treatment with ammonium citrate having been established, a series of tests was made to determine the effect of different solutions of ammonium citrate. Just prior to this, however, two samples of acid phosphate had been sent to twelve laboratories together with some of a solution of neutral ammonium citrate, with the request to determine insoluble PzOs using this citrate solution and also using their own. The average of the twelve tests on the ammonium citrate solution sent from this laboratory showed a ratio of ammonia
&
,
INDUSTRIAL A N D ENGINEERING CHEMISTRY
1038
to citric acid of 1 : 3.759. The average results for insoluble from the twelve laboratories follow: -PERCENT INSOLUBLEMinimum Maximum Av. S a m p l e I-Well-cured acid phosphate Citrate solution: Other laboratories.. . . . . . . . . . . . 0 . 0 8 0.29 0.18 Author’s laboratory . . . . . . . . . . 0 . 0 6 0.29 .... S a m p l e J--16 per cent arid phosphale Citrate solutions: Other laboratories . . . . . . . . . . . 0.730.95 0.88 0.95 . . . . Author’s laboratory . . . . . . . . . 0.74
Nine laboratories reported results in close agreement on the first report, and after further work and observing the precautions of thorough preliminary washing, all agreed within
Vol. 15, No. 10
Similar tests were made on a mixture of equal parts of acid phosphate and bone meal, when the effect of adding ammonia or citric acid to a neutral solution of ammonium citrate was more marked. It was found important to select a long-stem ( 5 t o 6 inches), 60-degree funnel for the preliminary washing, and with a carefully fitted paper the washing up to 250 cc. may be done in 20 to 30 minutes. It was further noted that when this precaution is not observed and an hour or more is required for washing, the results for insoluble are generally higher. (Some analysts add a little paper pulp or asbestos to increase rapidity of washing.)
PERCENT INSOLUBLE -Using Neutral CitrateVolume Preliminary Washing 100 Cc. 150 Cc. 250 Cc.
. , ..
1.20
1.12
1.09
Sample L-16%
Acid phosphate from Florida rock
0.30
0.25
0.28
Sample M-Acid
phosphate from Tennessee rock
0,37
0.30
0.25
3.77
3.65
3.61
....
....
0.25
Sample K-Mixed
fertilizer, 2 : 10 : 10.. ,
,
.
,
,
Sample N-16% Acid phosphate plus lime . . . . . Sample 0-Mixture acid phosphate and cottonseed m e a l , . ................................
Using Neutral Citrate Plus Ammonia or Citric Acid (Preliminary Washing 250 Cc.) Containing Excess Ammonia or Acid as Follows 0.5% 1.0% 2.5% 5.0% 10.0% NH40H 1.08 1,lO 1.10 1.11 1.11 C’itric acid 1 ,08 1.02 1.00 0.95 0.95 0.25 0.25 0.17 0.16 0.16 Fzzfcid 0.23 0.21 0.20 0.18 0.16
{ { { %?izFcicid { NHiOH Citric acid NH40H { Citric acid
0.37 0.25 3.62 3.64
....
,,
..
0.27 0.20 3.62 3.59
.... ....
0.27 0.15 3.67 3.51 0.23 0.23
0.28 0.14 3.97 3.44 0.25 0.21
0.27 0.12 4.12 3.33
.... ....
0.05 per cent. It was found that the difference was not due to ammonium citrate solutions, since the laboratory reporting the lowest results, likewise the one reporting the highest results, found the same with both solutions. Sample K was then prepared and portions sent to ten laboratories. This was a sample of mixed fertilizer containing about 2 per cent “3, 10 per cent available P z O ~and , 10 per cent K20. The results reported varied from 1.00 to 1.21 per cent, averaging 1.08 per cent. I n order to determine the effect of using a neutral solution of ammonium citrate as compared with solutions containing excess ammonia and others containing excess citric acid, the foregoing tests (Samples K to 0) were made.
M i n y other determinations were made by using different grades of filter papers, varying the temperature of the wash water, diluting before precipitation, etc., but none of these changes affected the results appreciably, especially as compared with the importance of thorough preliminary washing of the sample. ACKNOWLEDGMENT
An Improved Stopcock’
ing the low- and high-pressure valves) is bolted on tightly, so tightly that the plug can hardly be moved. After this the bottom flange, which before installation was fastened snugly, is tightened, thus relieving the pressure on the plug which is taken up in the top and bottom packing. The bottom flange is tightened just enough to secure easy movement of the plug. EASYHANDLING-In case the valve “sticks,” due to wear, the top flange is slightly loosened and the bottom flange tightened, thus securing a very quick repair without danger of the operator breaking the stem or the house, because no force is used as hammering or twisting. This valve can be repaired without interfering with the operation. EASYCLEANING-The’tWO openings on both sides of the house make an effective cleaning possible without taking the valve out of the line. REPLACEMENTS OF PARTS-If, after long service, the plug iS worn out too far, it can be easily replaced by an oversize or new plug, which means a considerable cut in costs Top Gland., because the housing remains in the line. The high pressure valve is very well adapted for a boiler blowoff valve. It carries an extra safet y flange on top and if fitted with a diamond boring it complies with the government specifications, as it cannot be opened a t once to its full extent because the plug and the house have to warm up slowly to the same temperature before the plug can be turned easily. FIG 2
By P.H.Kollewyn MARTINEZ, CALIF.
HIS little article is written to introduce to chemical engineers who have experienced trouble with leaking valves an improved stopcock which does not leak if properly handled. It has all the advantages of the regular stopcock, as easy adjustment, quick opening and closing, without the disadvantages of sticking and subsequent hammering or twisting off of the square top of the stem. This stopcock was invented2 as a result of trouble arising from the frequent replaceFT?--.---H@nd/e ments of valves in the acid lines of a California oil refinery. The first one was installed there in 1919 andis still in use. In Mexico this valve was used exclusively on all lines for corrosive liquids and also for steam and hotoil lines. The advantages of the double packed stopcock are: EASY INSTALI,ATION-After FIG. 1 1 2
the house is installed in the line the plug is put in and the top flange (see Figs. 1 and 2 show-
Received May 2. 1923. U. S. Patent 1,370,745(Mat.c h 7, 1921).
The author wishes to hereby express his thanks to H. C. Moore for many suggestions offered in this work, to those who have made many collaborative determinations, and his assistant, L. C. Smith, who has made a large number of careful determinations in the work.
