January 13, 1932
I N D U S T R I A L A N D E N G I N E E R I N G C II F -M I S T R Y
divided into units corresponding to 0.05223 A. Using this is equivalent to employing the equation log p,, = C/T B, where C is taken as the reading on the scale in question. 3. The vertical scale at the left side of the chart represents the values of B as given by the International Critical Tables. 4. The logarithmic scale on the right side gives the value of the vapor pressure in millimeters. 5. The point 100 on the P scale, indicated by the small circle. is used as a reference Doint in calcdatine 0.05223 A I T . 6. ’ The vertical scale withbut graduations wchd, if graduated, give values for 0.05223 A / T and C / T .
+
‘The chart is used in the following manner: Join the values of T and A by means of a straight edge, which will intersect
the undivided diagonal at some point. Then join this point with the reference point on the P scale; the prolongation of this line intersects the undivided C/T scale. Finally join this intersection with the value of B and read the vapor pressure on the P scale. This process will be made clear by a numerical example. To find the vapor pressure of isobutyric acid at 30” C., from the Int>ernational Critical Table, Vol. 111, page 219, we obtain the value of A as 48498 and B as 8.819. By following the procedure of the preceding paragraph the vapor pressure is found to be 2.85. This example has been worked on the chart, and the isopleths are shown by means of the
137
dotted lines and are numbered I, 11, and I11 in the order in which the points are connected. Using a slide rule and a six-place log table, we obtain 2.9 and 2.877, respectively, as the vapor pressure. From this alignment chart a reading of the vapor pressure of a substance may be made with sufficient accuracy for many purposes. If greater accuracy is desired, a larger chart with a smaller range can easily be constructed using the same principles. I n any case, however, this chart will serve as a valuable aid in checking calculations. The writers wish t o emphasize the fact that the large number of significant figures given in the constants A and B may be a trifle misleading, since vapor-pressure calculations are seldom made closer than one-tenth of a millimeter, except in the case of the more commoq substances where accurate tables have already been compiled. A chart employing these principles and covering the range of ethyl alcohol-water mixtures is in use in the writers’ research laboratories. LITERATURE CITED (1) Lipka, J., “Graphical and Mechanical Computation,” Wiley,
1918. RECEIVED Auguet 15, 1931.
Determination of Alkali in Glass R. D. SMITHAND P. CORBIN,Corning Glass Works, Corning, N . Y . HE r e a g e n t 8-hydroxywire o r s t i r r i n g r o d , t h e n T H E S U L L I V A N and Taylor oxalate quinoline (1)extends the evaporated to dryness (prefermethod with the additional use of &hydroxyusefulness, s p e e d , a n d ably in the special r a d i a t o r quinoline is particularly suited for alkali deaccuracy of the S u l l i v a n and described in the original method) terminations in borosilicate glasses and has Taylor ( 3 ) oxalate method for at a temperature just high additional uses in determining lime, alumina, the decomposition of glass and enough to expel the excess of the subsequent determinations oxalic acid. Before the end of and magnesia on the same sample. These deof alkali, since magnesia and e v a p o r a t i o n a loosely fitting terminations can readily be made in one day. o t h e r i n t e r f e r i n g oxides are platinum cover should be placed Larger samples can be used f o r alkalies, a point more readily removed from the on the crucible t o guard against of advantage in low-alkali glasses and glasses solution of the alkalies by the possible spattering. When all containing small amounts of lime, magnesia, organic reagent. This improved of the acid has been expelled, method is particularly valuable the crucible is cooled and the and alumina, etc., in determining their oxides. for simple borosilicate glasses evaporation r e p e a t e d once or The method is not recommended for glasses of of t h e P y r e x t y p e a n d i n twice more with oxalic acid and over 5 per cent alumina or materials of the general for silicates of not over water, depending upon the alufeldspar class. 5 per cent a l u m i n a c o n t e n t m i n a c o n t e n t of the glass. Double precipitation of the oxalates and which can be opened r e a d i l y The amount of oxalic acid used w i t h hydrofluoric a n d oxalic is about 5 grams, and should quinolates is recommended .for accurate alkali acids. The use of organic rebe noted for the blank deterdeterminations. This practice corresponds with agents permits the alkalies to mination. that of the J . Lawrence Smith method in double be weighed as chlorides. The REMOVAL OF PRECIPITATES precipitation or treatment of precipitates. method here described includes only the separation and deterOXALATE. A f t e r t h e last mination ofalkali, although attention is drawn to the useful- evaporation, when all of the oxalic acid has been expelled, ness of the method in removing, early in the analysis, in- the remaining oxalates are taken up with hot water, alsoluble oxalates (2) and quinolates, thus making it possible to lowed to cool, and filtered. The amount of water used for determine more speedily these oxides, lime, magnesia, and taking up the oxalates, washing the precipitate, etc., usualumina. ally amounts in all to not over 100 cc., and the crucible may be used to advantage as the extraction container, the DECOMPOSITION OF SAMPLE filtrate being caught in a Pyrex beaker of 150 to 250 cc. As in the original Sullivan and Taylor method, a 1-gram, capacity. or larger, sample of the ground glass is placed in a platinum At this stage, with a borosilicate glass free from lead and crucible of 40 cc. capacity. The glass sample is moistened second-group elements, no filtration is necessary to remove inwith water, 2 grams of oxalic acid and 20 cc. of 48 per cent soluble oxalates unless the small amounts of these elements, hydrofluoric acid added, the contents stirred with a platinum present as impurities, are to be determined. The %hydroxy-
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ANALYTICAL EDITION
quinoline reagent may be added directly to the total extraction from the crucible. With a lime or lead glass, however, the insoluble oxalates are filtered out and for accurate analysis dissolved in hydrochloric acid. The usual oxalate precipitation is then made after adding a few crystals of oxalic acid followed by enough ammonia to cause the solution to become ammoniacal. The second filtrate is treated separately with 8-hydroxyquinoline reagent and may contain no insoluble quinolates, in which event i t is saved for the final evaporation. QUINOLATE. The original oxalate filtrate or the entire unfiltered extraction from the last crucible evaporation, amounting to about 100 cc., is ready for the quinolate precipitation, A 5 per cent solution of 8-hydroxyquinoline in ethyl alcohol is used as reagent, from 10 to 20 cc. beingzequired depending upon the amount of oxides to be precipitated as quinolates. The reagent in excess will color the supernatant liquid yellow, Too large excess of precipitant should be avoided as it must be destroyed later. After the addition of reagent, the cool solution is made slightly ammoniacal dropwise with stirring, and allowed to stand in the beaker cooled by tap water for at least one-half hour. Filtration is then made using 1 per cent ammonia and a trace of the precipitant in the wash water. The filtrate is caught in a platinum dish and evaporated to dryness. The filtrate from the reprecipitation of oxalates is also added to the contents of the platinum dish, provided no insoluble quinolates are found present. I n addition, it is advisable for accurate work to reprecipitate the regular quinolate precipitate. The precipitate is dissolved in hydrochloric acid, excess 8-hydroxyquinoline added, and the solution made ammoniacal followed by cooling for one-half hour and filtration.
REMOVAL OF ORGANICMATTER AND CONVERSION TO ALKALI CHLORIDES The evaporated contents of the platinum dish are gently heated by passing the flame across the bottom of the dish until the organic matter and ammonium salts have been removed. The final stage of this decomposition is noted a t just under a red heat when the alkali oxalates bubble slightly, then remain as a quiet film of alkali carbonates. A cover glass should be placed on the dish upon cooling. After dissolving the carbonates in a little water and adding a few drops of hydrochloric acid, heat is applied again with the cover glass in place for a minute or two until the evolution of carbon dioxide and danger of loss of solution by entrainment is over. I n about 5 to 10 minutes the dish is dry and the contents are again taken up in a little water. Any organic char or silica is filtered out and the solution evaporated to dryness in a weighed platinum dish. Washington's (4) suggestion of adding a few drops of alcohol as dryness is approached is found to be excellent in causing the alkali chlorides to come down in such a form that decrepitation dangers are considerably lessened. The dish containing the alkali chlorides is gently ignited with a cover glass in position, being careful to keep below a; dull red heat, The alkali chlorides are weighed as sodium chloride and potassium chloride, and the usual potash determination can now be made and the sodium oxide determined by difference. A blank should be run on the method. On a 1-gram sample it was found that this blank amounts to 1 mg. of sodium chloride. Based on experience, the blank of the oxalate quinolate method is equivalent to only one-quarter that of the J, Lawrence Smith method under comparable conditions. Results with some Bureau of Standards glass samples are shown in Table I using the method just described on I-gram samples and comparing the weights of alkali chlorides thus
Vol. 4, No. 1
found with the equivalent chlorides of the recommended bureau analyses. TABLEI. COMPARISON WITH BUREAU OF STANDARDS VALUE (1-gram sample used)
BUR. OX.4LATE DIFFERENCE STANDARDS QUINOLATE Wt. of alkali NazO in VALUE METHOD Chlorides glass
GLASS Bureau No. 8 (sodalime magnesia glass)
Gram
Gram
Gram
%
0.3141
0.3138
-0.0003
-0.02
Bureau No. 89 (lead barium glass)
0.2406 0.2406
0.2416 0.2396
+0.0012 -0.0010
Some results on other glass samples analyzed in this laboratory using both the quinolate and J. L. Smith determinations are given in Table 11. TABLE11. COMPARISON WITH J. LAWRENCE SMITHMETriOD GLASS
(I-gram sample used) J. WT. OF NatO LAWRENCE OXALATZI ALKALI IN SMITE QUINOLATE CELORIDZISGLASS
1. Sodium borosilicate 2. Sodium borosilicate 3. Lead borosilioate 4. Barium calcium silioate 6. Bureau No, 91 (CaFz opal not standardized) Bureau No. 91
Qram 0.0926
0.0610
Qram 0.0930
0.0601
0 0848 0:3400'
0.0840 0.3394
0.2114 0.2116
0.2100
0.2098
Gram +0.0004 -0.0009
fO.02
-0.0008 -0.0006
-0.03
-0.0014 -0.0018
-0.07 -0.10
G ! ! I"
-0.05 -0.04
EXPERTMENTAL PROCEDURE I n order to study methods of separating alkalies from other elements remaining in solution after decomposing ordinary glasses, standard solutions were made up of the chlorides of aluminum, calcium, magnesium, sodium, and potassium. These solutions were tested by known methods for content of added constituent and for impurities of the other salts. The quinolate determination of alumina and .magnesia gave very satisfactory checks with the ammonia and phosphate gravimetric analyses, respectively. The alumina as determined on 5 cc. of the aluminum chloride solution was exactly 0.0118 gram by each method. Magnesia by gravimetric pyrophosphate determination, in 5 cc. of magnesium chloride solution, was 0.0091 gram, whereas by the quinolate gravimetric determination it was 0.0089 gram. This sample of synthetic solution was equivalent to: NaCl KC1
Grams 0.0626 (0.0010 gram NaCI in I-gram glass sample to 0.053% NazO) 0.0602 I _
Alkali chlorides MgO CaO A1201
HzCzOk
0.1227 0,0090 0.0266 0.0118 2,0000
Evaporation to dryness in a platinum dish was followed by fuming off the excess oxalic acid at 150" C. Duplicate samples were run by the new method without double precipitation of the oxalate or quinolate precipitates. These analyses showed errors of -0.0043 and -0.0030 gram of alkali chlorides, or on a l-gram glass sample -0.25 and -0.16 per cent sodium oxide. Starting with fresh samples, using a single oxalate and double quinolate precipitation, errors of -0.0029 and -0.0019 gram of alkali chlorides were obtained. These errors on a 1-gram glass sample would be equivalent to -0.15 and -0.10 per cent sodium oxide. Another sample was run using a double oxalate but single quinolate precipitation, and this showed an error of 0.0020 gram of alkali chlorides, or on a 1-gram sample of glass -0.11 per cent sodium oxide. Leaving out the calcium chloride solution and running still another sample of solution,
January 15, 1932
INDUSTRIAL AND E N G I N E E R I N G CHEMISTRY
omitting the oxalate separation and with a single quinolate precipitation, resulted in an error of -0.0023 gram of alkali chloride. A determination using no calcium chloride solution and omitting the oxalate precipitation but with a double quinolate precipitation, gave an error of -0.0004 gram of alkali chloride. These results indicate that it is desirable to reprecipitate both the oxalate and quinolate precipitates for accurate alkali determinations. The same applies to the J. Lawrence Smith determination, for it is extremely important to reprecipitate the calcium carbonate formed by ammonium carbonate, as otherwise a loss of several milligrams of alkali chloride may be suff ,fed. It A found that boric oxide is eliminated with the silica in the attack of the sample by hydrofluoric acid and oxalic acid, and that traces of fluorides remaining after the evaporations do not interfere in the separations. Sulfates when present may be removed with barium chloride and the barium removed as quinolate.
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Methods for determining the other oxides are not given, but references are given to articles describing the use of 8hydroxyquinoline. ACKNOWLEDGMENT It is a pleasure to record here appreciation of the interest and helpfulness of W. C. Taylor, chief chemist of the Corning Glass Works, in the work on this problem, and to acknowledge the helpful information obtained from G. E. F. Lundell of the Bureau of Standards. LITERATURE CITED (1) Eastman Kodak Co., Synthetic Organic Chemicals,4, No. 3 (Feb., 1931).
(2) Hillebrand, W. F., and Lundell, G. E. F., “Applied Inorganic Analysis,” p. 114, Wiley, 1929. (3) Sullivan, E. C., and Taylor, W. C., J. IND.ENG.CHEM.,6, 987 (1914). (4) Washington, H. S., “Chemical Analysis of Rocks,” 4th ed., Wiley, 1930. RECEIVED September 28, 1931.
The Bleaching Earths A Laboratory Study I
P. G. NUTTING, U. S. Geological Survey, Washington,D. C.
C
ERTAIN igneous rocks, such as granite, basalt, dunite, diabase, and many others, when exposed to weathering gradually break down both physically and chemically, the ultimate solid residue of the more profound types of weathering being largely inactive clays and soils. The original rock was composed of silicates high in bases, whereas the end products are secondary silicates, low in the more soluble bases but high in the oxides of iron and aluminum, and in silica. Midway on the decomposition curve are the products that are typical of the active bleaching or filtering earths. Some of our best fuller’s earth deposits are probably only the accumulated wash of partly decomposed igneous rocks which for some reason has not gone to soil or to inactive clay-typically the white and refractory clays. In a thoroughly weathered and partly leached condition, simple drying at 160” to 190” C. is sufficient to drive off adsorbed water, leaving the free valencies or open bonds essential to the bleaching or filtering action. When the leaching is less profound, acid treatment may greatly increase bleaching power. Some igneous dikes in Arkansas (1) decomposed in situ show decomposition to bleaching earth, to inactive ceramic clays, and to bauxite in neighboring parts of the same dike. Where the original rock was composed largely of the highly basic and complex minerals augite, hornblende, biotite, and (or) nontronite, the weathering was to fuller’s earth which was formerly mined and shipped. Where it was feldspar, it has decomposed to kaolin, and where it was nepheline it is becoming bauxite. Here in Washington are exposures of decomposed granite showing the three chief products just described within a few yards. Near Bull Run, Virginia, is a decomposed diabase having excellent bleaching properties after sifting and acidleaching. Only sedimentary deposits of bleaching clay are now being worked in this country, since these are abundant and the expense of screening is avoided. The chief sources are Georgia, Florida, southern Illinois, Texas, Colorado, Utah,
Kevada, Arizona, and southern California. Several plants mine and mill as much as 10,000tons per month. There is no production from glaciated areas. The bleaching clays were apparently brought down in large quantities of fresh water which kept the clay particles a t or near their isoelectric points. Thus, soluble bases were removed from their surfaces (and replaced by H and OH) but not completely from their interiors. Complete leaching of minerals low in iron, with long contact with fresh water, would result in kaolin. The western bleaching clays are less leached, and a few of them of the bentonite type require an acid leach to activate them.
PROPERTIES OF EARTH Neither chemical composition nor molecular structure as determined by x-ray analysis is sufficient to decide whether a mineral will be an active bleaching agent, since bleaching depends primarily on the condition of the surface rather than directly on composition or internal structure. The filtering material may be a simple hydrous oxide, a silicate, a glassy slag, ordinary glass, or volcanic ash. Activation may be said to consist in opening up the bonds over the surface (pores included) and the activity depends upon the extent of activated surface or number of open bonds per unit mass. As the writer has shown, it is possible to produce iron oxide, aluminum oxide, and silicon dioxide (2)in forms so active as to crack paraffin, and to activate the surface of even sea sand and crushed quartz crystals ( 3 ) . Among the commercial fuller’s earths, activities sufficient to crack paraffin, gasoline, or even the highly purified laxative oils are the rule. The bleaching or filtering action (decolorizing and deodorizing, chiefly) of the active earths on oils and other solutions varies greatly with the solution that is to be filtered and with the filtering material used. Hydrocarbons like petroleum, which contain no OH groups, require the assistance of heat to drive the OH from the filtering material. Either the earth is first heated to 180” C. (160” to 200” C.) and then used dry, or
