1216
ANALYTICAL CHEMISTRY
Very accurately reproducible microflow rates may be obtained by inserting one or more pieces of glass capillary tubing in series with the air-intake line, using rubber tubing connections. Glass thermometer tubing serves well for this purpose.
:
80-
APPLICATION OF MARIOTTE BOTTLE
The M,ariotte bottle has been utilized to calibrate a fine capillary flow-rate indicator in the flow-rate range below 100 cc. of gas per minute. I n this range the usual laboratory instruments, such aa a webtest meter, will not serve, and the Mariotte bottle affords a simple but accurate means of doing the job. The technique of calibration may easily be understood with reference to Figure 4.
c
W 2
16 PRESSURE DROP ACROSS CAPILLARY
Figure 5 . FLUSHED GAS
FLOW RATE INDICATOR
Figure 4.
Setup for Calibration
The discharge tip of the Mariotte bottle is connected to tube A . Water is then run into the graduated cylinder a t a fixed, invariable rate. The gas in the cylinder is thereby displaced and caused to pass through the capillary. To make the setu essy to handle, various refinements are incorporated. Stopcocf B is used to fill in the test gas a t the same time the foreign gas is being flushed out through stopcocks C and D. To prevent splashing and to smooth out the flow of water, the lip of the dis-
20
24
28
- CM B U T Y L PHTHALATE Two Calibration Curves
32
charge tube is provided with a very fine glass cat's-whisker which extends into the graduated cylinder. The drying bottle is used toapresent a moisture-free gas to the capillary. In Figure 5 are two calibration curves obtained with the arrangement shown ,in Figure 4. The upper curve refers t o hydrogen, the lower to air. The straight-line calibration holds good down to flow rates in the neighborhood of 5 cc. per minute and presumably lower. To test the accuracy of the work, the inverse ratio of the slopes of these two curves was compared to the ratio of the viscosities of the respective gases a t the experimental temperature of 25" C. The ratio of the viscosity of air to that of hydrogen at this temperature is 2.05, whereas the inverse ratio of the slopes is 2.06. There are several fine points to be considered if very high &ccuracy is required. In the first place, the solubility of the test gas in the water is of no importance, because the volume of the displaced gas alone is measured. But this displaced gas is watersaturated, so that the gas displacement rate of Figure 2 should strictly be corrected downward for the water vapor held up in the drying bottle. On the other hand, the gas is displaced at a pressure higher than atmospheric by the pressure drop across the capillary. The gas displacement rate of Figure 5 should accordingly be corrected upward if all gas volumes are to be referred to atmospheric pressure. These two effects therefore tend to cancel out and for most work' cdibration curves similar to those depicted in Figure 5 kill be adequately arcurate. RECXIVED December 22. 1949
Determination of Phosphorus in Alloys JA3IES I,. KASSNER
&ND
MARY ALICE OZIER, University of Alabama, University, Ala. REAGENTS AND STANDARD SOLUTIONS
HE analytical usefulness of the doublestrength citromolybT date solution which was used in the determination of phosphorus in iron ore (6)has been extended to include the determina-
The reagents for this method are essentially those used in t h e determination of phosphorus in iron ore (5).
tion of phosphorus in alloys. The analysis of several Bureau of Standards samples indicates that the accuracy and precision of this method are good, and average deviations in results are well within the range recommended for iron and steel analysis (3). Standard procedures other than those given may be used in dissolving the samples, provided that the volume of the solution before the addition of the citromolybdate solution is not over 80 to lo0 ml., and that the solution contains not more than 10 grams of ammonium nitrate or its equivalent in addition to not more than 6 ml. of concentrated nitric acid (specific gravity 1.42) or not more than 6 ml. of 60y0perchloric acid. The mixed indicator ( 4 ) used in the determination of phosphorus pentoxide in phosphate rock is used in determining the end point.
Steels Soluble in Nitric Acid. The procedure for dissolving the steel samples is essentially that adopted by the American Society for Testin Materials ( 1 ) and others ( 7 , 9). The volume of acid should be fetermined by the size of the sample, so that it will not be necessary to use more than 8 ml. of concentrated ammonium hydroxide (specific gravity 0.90) in adjusting the acidity. From this point, proceed as in the determination of phosphorus in iron ore ( 5 ) (Table I). Steels Insoluble in Nitric Acid. Weigh out a 0.5- to 2-gram sample of the steel into a 400-ml. beaker, add 30 ml. of hydrochloric-nitric acid (IO)mixture and 0.5 to 1.0 ml. of hydrofluoric acid, and heat on a hot plate until the sample is in solution and t h e silica is volatilized ( 1 ). Add 30 ml. of 60 to 70% perchloric acid, evaporate to fumes of perchloric acid, and fume for 5 to 10
DETERMMATION OF PHOSPHORUS IN STEEL
1217
V O L U M E 2 2 , NO. 9, S E P T E M B E R 1 9 5 0 Analyses of Standard Steels, Soluble in Nitric Acid Bur. Stds. Sample Phosphorus Value, % Deviations, .~ XO. Type Certified Exptl." %
Table I .
1Oe
86
B a s e mer s tee1 Beseemer steel
0.093 0.083
129.4
Bessemer steel
0.094
1 le
B.O.H. steel
0.015
15D 21c
B.O.H.steel
0.018 0.062
a
.4.O.M. steel
0.000
0.093 0.083 0.081 0.091 0.098 0.091 0.015 0.012 0.017 0.060 0.063
0.000 -0.002 -0,003
+0.004
-0,003 0.000 -0,003 -0.001 -0.002 +0.001
Time of boiling for complete precipitation about 5 minutes.
..
Table 11.
.4nalyses of Standard Steels, Insoluble in Nitric Acid
Bur. Stds. Sample _..-.___
.
SO.
3Oc
Type Cr-V steel. V 0.2357,
34b
Cr-Ni steel
100
hln rail steel
106.i
Cr-Mo-Al steel
IllA
Ni->Mo steel
121.i
Stainless stee!. 18% Cr, 10%,Ni, titanium bearing
Phosphorus Value, % Cert,ified Exptl.a 0.019 0.020b 0.021; 0.014 0.016 0.015 0.014 0.023 0.020 0.021 0.016 0.018 0.014 0.017 0.020 0.016 0.023 0.020 0.022
is in solution except for a white residue. Add 15 ml. of hot water and digest at 80 to 90" C. until the residue goes in solution. Dilute to about 80 ml. with water, add 100 ml. of double-strength ritromolybdate solution, heat to boiling, and boil for 5 t o 10 minutes. From this point, proceed as in the determination of phosphorus pentoxide in phosphate rock ( 4 ) (Table IV).
Deviations,
DISCUSSION AND NOTES ON PROCEDURE
In using the perchloric acid procedure as outlined for steel, i t was found unnecessary to adjust the acidity by adding ammonium hydroxide when the volume of perchloric acid used did not exceed 30 ml. of 60 to 70qc avid. IVhen the sample contained a large amount of vanadium, it NXS found advisable to add 150 ml. of the citromolybdate solution and allow it to stand overnight before filtering. If arsenic is present in large amount, it should be removed as recommended by Lundell, Hoffman, and Bright ( 6 ) .
% +0.001 +0.002 -0.005 -0.001 -0.002 -0.oox -0.002 +o 002
ACKNOWLEDGMENT
This research was sponsored by a grant from the Research Fuiill of the University of Alabama.
Table 111. Analyses of Standard Cast Irons
-0,002
-0 001
NO.
-0.003 -0.001
4g
Time of lmilina for complete precipitation 10 to 15 minutes. Reduced w i t h ferrous sulfate, allowed to stand overnight before filtering, 1,jO ml. of douhle-strength citromol bdate solution used. r Reditred with ferrous sulfate, zltered iinnlediately, 150 rnl. of douhlertrrngtli ritromolybdate solution used.
6d
'I
1,
7c
89
ininutes. Cool, add 50 ml. of h-ater and a saturated solution of sulfur dioxide or sodium sulfite until chromium and vanadium are reduc-ed, and boil until all the sulfur dioxide has been expelled.
From this point, the procedure for the determination of phosphorus in steels insoluble in nitric acid is the same as that for qteels soluble in nitric acid, except that the boiling time for complete precipitation is 10 to 15 minutes (Table 11).
IO?
115 b C
Pliospiiorus Value. % certified Exptl.a 0.121 0.126 0.123
Bur. Stds. Sample Type Cast iron
+0.003
Cast iron, As 0 . 2 6 %
0.486
DETERMLWATION OF PHOSPHOHUS IN CAST IRON
I)ETERMINATION OF PHOSPHORUS IN FERROPHOSPHORUS
Prepare a 1-gram sample for analysis as described by Lundell, floffnian, and Bright (81, and dilute to 500 ml. in a volumetric flask. Pipet a 25-ml. aliquot into a -100-ml. beaker; add 50 ml. of water, 3 to 5 ml. of conrentrated nitric acid (specific gravity 1.42), and 3 to 5 ml.of 2.5y0 solution of potassium permanganate; :ti>dboil carefully until manganese dioxide is precipitated. .4dd a saturated solution of sodium nitrite, dropn-ise, until all the mangxiiese dioxide disappcars. Boil to expel oxides of nitrogen, add 100 ml. of double-strength citromolybdate solution, heat to boiliiig, and boil 5 to 10 minutes. From this point, proceed as in the determination of phosphorus pentoxide in phosphate rock ( 4j (Tahle IV). PROCEDURE FOR PHOSPHORUS IV PHOSPHOR BRONZE
Keigh out a 2-gram sample of phosphor-bronze bearing metal iiito a 400-ml. beaker, add 15 ml. of concentrated nitric acid (specific gravity 1.42) and 5 ml. of concentrated hydrochloric acid (specific gravity 1.19), and heat on a hotplate until the sample
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% +0.00:1
+0.002
+0 . 0 I6 4-0 0 16 ;, h
0.502 , 0.474 -0.712 Cast iron, 0 778 0.787 +O.OOD' As 0.071% 0.791 +0.013c 0.796 +0.018h 0.806 +o. 0 2 8 h Xi-Cr cast iron 0 102 0.104 +o.onz 0.103 +0.001 Ni-Cr-Mo cast iron 0.197 0.195 -0.002 0.195 -0.002 Cu-Ni-Cr cast iron 0.113 0.107 -0.006 0.107 -0.006 Time of boiling for complete previpitation about 5 minutes.' -4rsenic not removed; 100 mi. of double-strength citromolybdate used. Arsenic not removed; 40 nil. of double-strength citromolybdate used. ~~
Table IV.
Analyses of Other Bureau of Standards Sample*. Phosphorus Certified
Sample
The samples were dissolved according to the standard procedure (t,1I ) , precipitated, and titrated as when determining phosphorus in steel (Table 111). The nitric and perchloric acid procedure ( I 1 j, which is similar to the procedure for steels insoluble in nitric acid, can be used for cast iron.
0.502
~
Value. 'lo
TyPe Ferrophosphorus
NO.
90
26.2
Phosphor-bronze bearing metal
63
0.62
Phosphorus Exptl. Value, % 26.2 26.2 0.61 0.61
Deviation,,
% 0.0
0.0 -0.01
-0.01
LITERATURE CITED Am. SOC. T e s t i n g Materials, Philadelphia, P a . , " M e t h o d s of' Chemical Analysis of M e t a l s , " p. 1 9 , 1939.
Ibid., p. 20. Campbell,
E. D., a n d S m i t h . G . F.. J . I n d . Eng. Chern., 12, 10%)
(1920). K a s s n e r , J. L., C r a m m e r , H . I>.. a n d Osier, 11.A., ANAL.C H E M . , 20, 1052 (1948). K a s s n e r , J. L., a n d Oaier, M. A , , Ibid., 22, 194 (1950). Lundell, G. E. F., H o f f m a n , J. I., a n d Bright, H. A., " C h e m i r n l Analysis of Iron a n d S t e e l , ' ' p. 213, New York, J o h n Wiley B Sons, 1931. Ihid., p. 223. Ibid., p. 438. U. S. Steel Corp., "Sampling a n d Analysis of C a r b o n a n d Alloy Steels," p . 89, Xew York, Reinhold Publishing Corp., 1938. I b i d . , p. 90. U. S. Steel Corp., "'Sampling a n d Analysis of P i g I r o n a n d C a s t Iron," 3rd e d . , p. 47, P i t t s b u r g h , Carnegie Steel Co., 1934. '
RECEIVED December 2, 19.19. Presented before the Fourth Annual .4nalytical Symposium, Pittsburgh Section, . ~ Y E R I C A N CXEMICAL SOCIETY.Pittaburgh, Pa., January 21, 1949.
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