T H E JOURA’AL OF I-VDb-iSTRIAL A N D E-VGINEERIATG C H E M I S T R Y
Feb., 1913
I
-x
= proportionpf
Bb
(I-%)
incident light entering b, film.
+ ~ + a ,= c =
I
x fa,
123
the different white pigments, tested on the formula given above, are shown. The values for P are the coefficients of opacity as defined above. The reflection is the proportion of incident light reflected and is expressed in decimals of unity. Coefficient of Pigment. opacity P White lead-Dutch.. . . . . . . . . . . . . . 0.0671 White zinc--American process.. . . . 0.0794 White zinc-French Pr. . . . . . . . . . . 0.0645 0,0578 Lithopone.. . . . . . . . . . . . . . . . . . . . . . Calcium carbonate. . . . . . . . . . . . . . . 0.0136 Basic lead sulphate.. . . . . . . . . . 0.0813 China clay. . . . . . . . . . . . . . . . . . . . . . 0.0190 Asbestine. . . . . . . . . . . . . . . . . . . . . . . 0.0090 Calcium sulphate.. . . . . . . . . . . . . . . . 0.0030 Silica., . . . . . . . . . . . . . . . . . . . . . . . . . 0.0102 0.0114 Barytes.. . . . . . . . . . . . . . . . . . . . . . . .
-1
from which
Reflection’ 0.935 0.956 0.964 0.947 0.969 0.927 0,823
0.859 0.856 0.793
0.856
This work was done in the research laboratory of the National Lead Co., much of it having been accomplished with the assistance of one of my associates, Mr. R. L. Hallett, to whom I tender thanks.
This formula looks rather complicated, but, in practice, and b y the use of logarithmic tables, the work is more simple than it seems on first inspection. The apparatus to which I refer reads to the one tenthousandth of a n inch and, preferably, should have been constructed with the millimeter scale. It is a simple matter, however, to make conversions into the mm. scale. I n making these calculations, it is t o be observed that, the comparison of the pigments having been made between glass surfaces, the amount of light reflected from the adjacent surfaces of a paint would probably be different from the light reflected from the surface of paint which is adjacent to air. This is a controlling reason why the reflected light should not be considered in calculating the coefficient of opacity. I n testing pigments for their coefficients of opacity, we have followed the plan of mixing these pigments with linseed oil on a standard formula of 2 5 per cent. by real volume of pigment and 75 per cent. by volume of oil. I n some cases, as, for instance, in the case of zinc oxide, this may be too large a volume of pigment, to handle conveniently in the apparatus; but, if trouble is experienced, a different formula can be used, comparing i t with another standard pigment on this changed formula. This apparatus is somewhat new and me have not as many results t o report of work done upon it as could be desired, and what we present here is simply for information; and, so that the subject may be more generally studied, we present here some determinations made in this apparatus, working on a number of white pigments. I t is not t o be supposed that these tests represent average pigments or that thc results presented are for the purpose of condemning any of the pigments tested. It is very probable that the pigments upon the market, of the kind described, vary considerably from the figures presented here. The coefficients of opacity and the light reflected by
AN APPLICATION OF THE ELECTRIC RESISTANCE FURNACE TO THE DETERMINATION OF OXYGEN IN IRON AND STEEL B y R . H. MCMILLEN Received January 6, 1913
’
The fact that iron and steel always contain more or less oxygen has long been known, and about thirty years ago, Ledeburr called attention to i t and gave a method for its determination. I t is only recently, however, that the requirements in the manufacture of high-grade steels have become so exacting that the determination of oxygen in steel and other materials has come to be one of the routine determinations required of a steel laboratory. The Ledebur method, which is well known, consists in heating the sample of iron or steel in nitrogen to remove all moisture without oxidizing i t , then reducing the oxides a t a red heat by hydrogen and absorbing and weighing the resultant water. Cushmanl has shown that the drying of the sample in nitrogen is unnecessary, his results being but slightly higher than those by the original method. When used with electric resistance furnaces, this method is very satisfactory for the determination of oxygen in iron and steel, tungsten,~and other non-volatile metals. Even this method, however, will fail t o show all the oxygen in metals containing oxides of silicon, vanadium, titanium, and other elements whose oxides are not reduced below 950’ C.4 The following modification of the Ledebur method has been found to give most satisfactory results: APPARATUS
The apparatus consists of two electric resistance Sauerstoffbestimmung im schmiedbaren Eisen, Stahl u.Eisez, 2, 193. “The Determination of Oxygen in Iron and Steel,” THISJOURNAL, ‘3, 372. 3 Tungsten powder often contains a rather large percentage of oxides. Some commercial samples investigated by the writer recently have shown an oxygen content corresponding t o 12 per cent. WOa. I t is probable, however, that the whole of the oxygen is not combined with the tungsten. 4 See “The Determination of Oxygen in Iron and Steel, b y Reduction in an Electric Vacuum Furnace.” by W. H. Walker and W. A . Patrick, THISJOURNAL, 4, 799. 1
124
.
T H E JOURzV.4L OF I N D U S T R I A L 4;YD E.VGI.VEERI:YG
CHEMISTRY
Feb., 1913
furnaces, such as are employed in many steel laboratories for combustion carbon determinations and capable of maintaining a temperature of 950' C. They are designated as S o . I and No. z in the illustration, Both furnaces are equipped with heavy-walled, fused quartz tubes 7 / a inch inside diameter by 2 4 inches long. The function of furnace No. s is to heat the sample under investigation, while that of No. z is to heat the hydrogen so that it may combine with any oxygen that may be carried over from the hydrogen generator. Several spirals of platinum gauze are placed in the quartz tube of this furnace. The quartz tubes of these furnaces are connected in the rear by a U tube (not shown in figure) having close-fitting glass stopcocks This U tube is filled with phosphorus pentoxides opened by small glass heads. The phosphorus pentoxide absorbs any water which may he formed in the tube of furnace No. 2 , and insures absolutely dry hydrogen to pass over the sample in furnace No. I . The front end of the quartz tube in No. z
so that they he free from rust or foreign oxides. In the case of iron or steel samples both the fine and coarse drillings are rejected, only those between twenty ( 2 0 ) and thirty (30) mesh being used. These are dried for at least one hour over concentrated sulfuric acid before using. Samples of tungsten powders are dried to constant weight in the drying oven a t a temperature of roj" C.
furnace is connected to the drying and purifying train leading from a hydrogen generator. No. 3 contains small pieces of pumice stone saturated with concentrated sulfuric acid, No. 4 soda lime, No. j stick potassium hydrate, No. 6 a 5 0 per cent. solution of potassium hydrate, No. 7 a zj per cent. solution of pyrogallol made alkaline with potassium hydrate. Hydrogen is generated in a sixty-four (64) ounce Kipp apparatus by the action of chemically pure hydrochloric acid on pure mossy zinc. The water formed by reduction of oxides in the sample is absorbed in U tube No. 9 of same construction as No 8 , and also filled with phosphorus pentoxide opened with small glass beads. A guard tube, No. I O , is attached to No. 9 and contains concentrated sulfuric acid. A small wash bottle of the Drexel form is used for this purpose. Porcelain boats of sufficient size to hold a t least twenty-five ( z j) grams of the sample are employed.
expulsion of oxygen from the train and tubes. The train and quartz tube of furnace No. z can be kept constantly filled with hydrogen by closing the cocks of U tubes No. 8 whenever the fiow of hydrogen is interrupted. The electric current is turned on and continued for one hour after the maximum temperature has been reached, During this time the flow of hydrogen is cut down to about seventy ( 7 0 ) bubbles per minute, this rate being maintained until U tube No. 9 is removed. At the end of the hour the current is turned o f f and furnaces allowed to cool, accelerating the cooling with a blast of compressed air. When the quartz tubes in the furnaces show no visible redness, the cocks of U tube No. g are closed and a pinchcock is inserted over the rubber tube connecting U tube No. g to the quartz tube of furnace. I n this manner oxygen is kept from the heated tube, thereby avoiding danger of explosion. U tube No. g is disconnected and carefully wiped with a soft, dry cloth then desiccated over concentrated sulfuric acid for fifteen min-
PREPARATION OF SAMPLE
.
Great care must be taken in preparing the samples
PROC.EDURE
Twenty-five ( 2 s ) grams of the prepared drillings are weighed into the dried porcelain boat and placed in the tube of furnace No. I. Connection is made to the weighed U tube, No. 9, through which, just previous to drying for fifteen ( I S ) minutes and to weighing. hydrogen has been passed for ten (IO) minutes. Guard tube No. so is connected. Hydrogen is allowed to pass through the whole apparatus a t a rapid rate for fifteen ( I j) minutes. For the first run it is advisable to allow the hydrogen to sweep through the whole apparatus for thirty ( 3 0 ) minutes to insure complete
Feb., 1913
T H E JOLTRA\.\-.4L OF I-VDUSTRIAL A N D ENGINEERING CHE.WISTRk t
Utes and finally quickly weighed. Weight of water, after deducting blank, multiplied b y 0.8888 divided b y 2 5 equals oxygen. A blank should be run frequently, adhering t o all details as t o time of heating furnaces, desiccating U tube, etc. Usually the blank found varies between 0.0015a n d 0 . 0 0 2 5 gram. For samples of tungsten powder the same procedure is carried out except that a smaller sample is taken varying from one t o ten grams according t o the amount of oxygen present. The following table gives results on several samples in duplicate by the above described procedure : Oxygen C
NO.
Mn
S
P
. . . . . . 1.15 0.31
Si-
0.018 0.011 0.015 0.010 3 Crucible steel.. 1.14 0.33 0.016 0.009 41 Basic open hearth steel.. 0.07 0.06 0.019 0.008 5 Basic open hearth steel., . 0 .OS 0.22 0.016 0.008 6 Swedish wrought iron. , . . 0 . 0 6 0.17 0.019 0.012 7 Domestic wrought iron.. . 0.69 trace 0,009 0,007 8 Domestic wrought iron... 0.73 . . 0.009 0.007 9 Acid open hearth steel.. .. 0.36 0 . 6 9 0.040 0,046 10 Bessemer steel.. 0 . 4 6 0.72 0.041 0.095
......
..........
1 . 1 7 0.31
.
......... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1
0.22 0.039 0.037 0.22 0.035 0.035 0.21 0.044 0.045 0 .OS 0.113 0.115 0.01 0.079 0.072 0.02 0.345 0.353 0.06 0.069 0.076 0.06 0.090 0.089 0.03 0.043 0.042 0.09 0.058 0.060 . . . 2.57 2.57 . . . 1.37 1.34 . . . 0.55 0.56 . . . 1.02 1.05
This sample fractured badly in rolling.
Numbers I, 2 and 3 were three ingots made under as nearly the same conditions as possible. It is not intended t h a t the above table should be typical as to the oxygen content t h a t exists in the different classes of steel. I n many samples of crucible steel it is much lower than those cited. CRESCENTLABORATORY CRUCIBLESTEELCo. OF AMERICA ASPINWALL,PA.
THE VOLUMETRIC DETERMINATION OF MANGANESE IN ROCK, SLAGS, ORES AND SPIEGELS . B y F. J. METZGERAND L. E. MARRS Received November 1, 1912
A new and accurate method for the determination of manganese and its application t o the analysis of iron and steel has been published by us in THISJ O U R N A L (3, 333). The method has since been applied to rock, slags, ores, and spiegels and it is the purpose of this paper to report on these. Analyzed samples of rocks and of a manganese ore were furnished by W. F. Hillebrand, of the Bureau of Standards. We desire to express our gratitude t o Dr. Hillebrand for this material assistance and for the kindly interest he has shown during the progress of our work. Rock.-Here the manganese content is a p t to be very low and for accurate work a portion of from two to five grams should be taken for analysis. Place the weighed portion in a platinum dish; add 5-15 cc. dilute sulfuric acid (I : 2) and boil; add 5-15 cc. hydrofluoric acid and boil until the rock is completely decomposed. Add 5-10 cc. dilute nitric acid ( I : I) and 2 or 3 cc. of concentrated sulfuric acid; remove from the flame and add about one gram ammonium persulfate in small portions: when evolution of gas has ceased, evaporate t o fumes of sulfur trioxide,
125
cool, add 5 0 cc. water, boil and cool. Transfer t o a wax beaker, add 5 grams ammonium fluoride and 2 5 cc. hydrofluoric acid (making a total volume of about I O O cc.) and titrate t o a permanent pink color with potassium permanganate solution (approximately
N/30). The value of the permanganate in terms of iron multiplied b y 0 . 7 8 6 8 2 gives the value in terms of manganese, or by 1.01601in terms of MnO. Slag.-Weigh out 0.2-1.0 gram and treat as in rock unless the manganese content is high. If more than about 20-30 mg. of manganese is present in the solution titrated, a brown color will appear toward the end of the titration, but, with a very little experience, as much as 60 mgs. may be titrated with accuracy using a N/IO(approx.) permanganate solution. With high percentages of manganese, the titration of a n aliquot part of the solution is much more accurate than weighing out exceedingly small amounts. I t has been found best to titrate with a volume of about 150 cc. containing about 60 mgs. of manganese when more than 40 per cent. of manganese is t o be determined. If much manganese is present in the solution. oxidized manganese compounds may appear after the addition of the nitric acid t o the mixture; the authors have found, on several . occasions, a strong permanganate color on taking the mixture to fumes of sulfur trioxide. When this occurs, cool; add 50 cc. water; cool again; add hydrogen peroxide (drop b y drop) until the color disappears; boil about ten minutes, cool, and titrate as usual. Ores.-Pyrolusite : Dissolve 0.5-1.0 gram of the ore in a casserole, using as small a quantity of dilute hydrochloric acid (I : I) as possible. Add 15 cc. dilute sulfuric acid ( I : 2) and evaporate t o fumes of sulfur trioxide.1 Cool and add I O cc. dilute nitric acid ( I : I ) and about I gram of ammonium persulfate (have the casserole covered). After evolution of gas has ceased, remove cover and take to fumes of sulfur trioxide. Cool, dilute with water, cool again, transfer t o a 2 5 0 cc. flask and dilute t o the mark. Take a n aliquot portion (preferably not less than 0.1 gram of the original ore) and titrate in a volume of about I jo cc., containing 5 grams ammonium fluoride, I O cc. dilute sulfuric acid (I : 2 ) and 2 5 cc. hydrofluoric acid. Ores, Slags, etc., Insoldde in Hydrochloric o r Nitric Acid-Proceed a s in rock, using peroxide treatment if necessary. Spiegels (and Ferromanganese).-Weigh out 0.2-1.0 gram and dissolve in 5-10 cc. dilute nitric acid (I : I ) in a covered casserole; cool slightly and add I gram ammonium persulfate; when action has ceased, remove cover, add 15 cc. dilute sulfuric acid (I : 2 ) and evaporate almostz t o fumes of sulfur trioxide ; cool, add 50-100 cc. w a t e r ; ~heat until ferric salts are All hydrochloric acid must he removed as titrations made with even small amounts of HC1 were decidedly inaccurate. Nitric acid up t o 2 cc. concentrated acid in a volume of 150 cc. has no effect on the titration. If any oxidized manganese appears here, treat with hydrogen peroxide a s described under Slag.
*
I
