Mar., 1916
T E E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
according t o G. Rothaug,l t o t h e precipitate absorbing atmospheric oxygen during ignition with t h e formation of chromic chromate (CrZ03.3Cr03). If ignition takes place i n a current of hydrogen, accuracy will be secured. In t h e absence of sulfates t h e author used t h e following method t o check u p t h e volumetric method a n d obtained results agreeing very closely. T h e sample is fused as i n t h e volumetric method, t h e n dissolved out a n d made neutral with acetic acid, 0.5 cc. glacial acid is added i n excess and t h e solution diluted t o 400 cc. T h e chromate is precipitated a t t h e boiling t e m perature with a dilute solution of barium acetate. The barium acetate should be added b y drops so a s t o avoid carrying down some of t h e barium acetate with t h e barium chromate. After t h e precipitate settles i t is filtered off on a Gooch crucible, washed with dilute alcohol a n d dried. CHEMICAL LABORATORY, G. SIEGLECOMPANY ROSEBANK, STATEN ISLAND, N E W YORK
THE SOLUTION OF THE CERIUM GROUP OXIDES BY CERTAIN ACIDS By W. S CHASE Received September 13, 1915
As is well known, t h e oxides of t h e trivalent rare e a r t h metals afe moderately strong bases, resembling t h e alkaline earth oxides in t h a t respect. With this fact in mind, one would expect t h a t t h e addition of a dilute mineral acid to a mixture of cerium group oxides would effect t h e quick solution of t h e more basic earths with b u t slight action on t h e least basic. If this did occur, t h e result would be t h e complete separation of CeOz, which is t h e least basic of all t h e rare earth oxides a n d very resistant t o acids. Such a separation, which indeed would constitute a rapid a n d easy method for t h e extraction of cerium, might be expected when it is considered t h a t t h e other oxides present are, for t h e most p a r t , a m o n g t h e more basic of t h e rare e a r t h oxides.2 Unfortunately, t h e addition of dilute or even concentrated acid does not produce t h e expected result, a n d this must be due t o t h e influence of t h e CeOz. This substance is practically insoluble even in hot concentrated acids, except sulfuric acid. It possesses t h e power of combining with t h e other rare earth oxides, a n d t o this combination is undoubtedly due t h e failure of acids t o react with t h e mixt u r e of oxides in t h e manner t h a t might be expected. Another result of this combination is t h a t t h e CeOz, when t h u s combined, dissolves readily in acids i n which i t is otherwise insoluble provided its value in t h e mixture does not exceed 55 per cent. Therefore, on treating t h e mixed oxides with acid t h e basic earths do not rapidly dissolve a n d t h e CeOZremain untouched, b u t , instead, t h e entire mixture goes into solution a t a moderately rapid rate. This behavior is rather remarkable in view of t h e fact t h a t CeOz itself is practically insoluble, a n d t h a t t h e other oxides b y themselves will dissolve instantly in a small excess of very dilute acid. T h e r a t e of solution of t h e mixed oxides can be very 1 2
Z . anoyg. Chem., 84 (1913). 165-189. Levy, “The Rare Earths,” pp. 117, 118
239
greatly increased b y t h e addition of some substance t h a t will reduce cerium t o t h e cerous condition. Hydrogen peroxide answers this purpose admirably, for. not only is t h e reaction very rapid a n d complete b u t there is t h e added advantage t h a t no other salt is introduced into t h e solution (as is t h e case for example when KI or PeCl2, etc., are used). EXPERIMENTAL
T h e rare e a r t h residue obtained after t h e extraction of thorium from monazite sand was t h e material used in this work. This residue consists essentially of t h e oxides of t h e cerium metals though possibly small quantities of t h e y t t r i u m elements may be present. N o a t t e m p t was made t o separate t h e latter as t h e y were not in sufficient quantity t o be detrimental in a n y way. T h e principal constituent of t h e mixed oxides was, of course, CeOZ,with a value of 5 2 . 7 0 per cent, t h e others, in order of importance being NdzO3, Laz03, Pr407 a n d SazOa. T h e composition of t h e ordinary commercial residue is quite constant, t h e CeOs value for instance fluctuating between j o a n d 60 per cent, a n d in most cases being around t h e mean of those values. T h e color of t h e mixed oxides varies from reddish brown t o chocolate, depending on t h e composition of t h e sample, ignition temperature,* etc. Their solubilities in sulfuric, hydrochloric, nitric a n d acetic acid of different concentrations were studied, as was also t h e use of HzOz as a reducing agent for CeOz. T h e theoretical quantity of acid required t o react with I g. of sample was calculated on t h e basis of ROZ = 5 5 per cent, R z 0 3 = 45 per cent (about t h e average composition of t h e residues handled in this laboratory) a n d t h e following figures were t h u s obtained: Sulfuric ACID Approximate strength.. . . . 9 6 % Cc. per 1-g. sample... . . 0 . 5 8
..
Nitric 70% 1.33
Hydrochloric
Acetic
38% 1.7
99.5% ’1.2
ACID-AS is well. known, with a large excess of acid a n d evaporation t o strong fuming, complete solution is obtained. T h e CeOz dissolves with b u t slight reduction, so t h a t t h e solution is of a yellow or yellowish red color due t o t h e ceric sulfate. However, this process is rather tedious! a n d as it is desirable t h a t t h e fuming operation be avoided, if possible, t h e action of H 2 0 2along with dilute HzS04 was tried. A few experiments sufficed t o show t h a t w.ith a moderate excess of acid diluted as much a s I : I O or more, and a similar excess of H~02, solution is rapid a n d thorough. For example, I cc. each of acid a n d 30 per cent HzOz a n d I O cc. of water were added t o I g. of t h e oxides a n d t h e mixture heated for 3 minutes, b y which time solution.was complete. This experiment indicates t h a t these oxides are dissolved b y dilule H z S 0 4 HZOZ much more rapidly t h a n by concentrated H 2 S 0 4 a l o n e , a n d further t h e fuming nuisance is also avoided. NITRIC ACID-The mixed earths dissolve fairly readily in this acid, which is most efficient when concent r a t e d . However, when diluted, even as much as SULFURIC
+
1
Levy, “The Rare Earths,” p. 119.
T H E J O U R N A L OF I N D C S T R I A L A N D ENGINEERING CHEMISTRY
240
I : 2 , it still acts fairly satisfactorily though somewhat slo~vly. When the acid alone is employed it is always necessary t h a t a considerable excess be taken, b u t the quantity of the latter naturally decreases as the size of the sample increases. With t h e smaller samples, in order t o avoid t h e use of a very great excess of acid, the same should be diluted, which serves t o increase t h e volume enough so t h a t all t h e acid. is not boiled off before complete solution can occur. These points are indicated by t h e following d a t a :
Sample used Grams 1 3
5
1
5
NITRIC ACID PSED Parts Parts Times acid Water theoretical I 2 6 1 2 4 1 2 3 1 0 8 1 0 6
Total cc. Minutes required of liquid for solution a t start (approximate) 24
48 60 10.5 40
The use of HzO2,however, produces results greatly superior, in every way, t o those obtained with the nitric acid alone, b u t especially so in regard t o speed of reaction and excess of acid. Solution occurs so quickly and completely t h a t even small samples can be readily dissolved in a slight excess of acid, it being unnecessary t o have a considerable volume of liquid a t t h e s t a r t , on account of t h e rapidity of the reaction. The following results indicate the advantages pertaining t o t h e use of H 2 0 2 . Practically t h e same results could be obtained with considerably more dilute acid. Sample used Grams
SOLUTION X~IXTVRE
1
Parts HiXOs 1
3
I
Parts water
H?02
T o t a l cc. of liquid a t start
2 1
0.5 1.5
10
Cc.
5
Minutes required for solution (approximate) 1 1
acID-The action of this acid about parallels t h a t of nitric, or if anything, it is somewhat more efficient, for although concentrated hydrochloric is only about one-half as strong as concentrated nitric acid, i t acts with equal speed. Owing t o its lesser concentration a larger volume is required for t h e same equivalent of acid t h a n with nitric, and it was found t h a t owing t o this, a smaller excess of hydrochloric could be used for a given sample t h a n is necessary when nitric is employed; e. g., a j g. sample which was readily dissolved by 4 times t h e theoretical amount of hydrochloric acid, required 6 times t h e theoretical quantity of nitric acid t o effect its solution. This behavior with hydrochloric acid was quite unexpected, t h e writer having always been under the impression t h a t these oxides were practically insoluble in it except in t h e presence of a reducing agent. T h e chloride ion apparently acts in t h e latter rble, free chlorine being given off during t h e reaction. H 2 0 nacts with hydrochloric acid in exactly the same manner as with nitric. ACETIC ACID-The acid used contained 9 9 . j o per cent HC2H302 and proved t o be a very unsatisfactory solvent for these oxides. I t s action is extremely slow, so t h a t long boiling, with t h e consequent necessity of a large excess of acid, is necessary in order t o obtain the solution of even a moderate amount of material: e. g , , a r-g. sample was treated with 2 0 times the required quantity of acid, the mixture heated t o boiling, then placed on the steam b a t h and frequently HYDROCHLORIC
SO.3
shaken; after half an hour t h e residue was filtered off, the filtrate precipitated with oxalic acid, a n d t h e oxalates ignited t o oxides; this oxide did not exceed more t h a n about 0.05 g. in weight. Very peculiarly H202 does not seem t o facilitate solution in this case, repeated experiments using large excesses of the peroxide giving no better results t h a n t h a t above noted. As suggested b y Dr. IT. C. Moore, of the Research Laboratory, this behavior may be due t o some reaction taking place between t h e hydrogen peroxide and the acetic acid itself. S U MM A R Y
7 20 20 4 10
Val. 8 ,
I-This investigation has shown t h a t t h e cerium group oxides are fairly readily dissolved b y sulfuric, nitric or hydrochloric acid, and especially so when t h e concentrated acids are used, although in t h e case of the latter two. considerable dilution still permits of satisfactory results being obtained. However, it is necessary t o use a considerable excess of the respective acid. and more particularly so if the sample is small and it is required t o dissolve it in concentrated acid. 11-Acetic acid was shown t o be a very unsatisfactory solvent. 111-The use of hydrogen peroxide makes rapid dissolving of the oxides b y a very small excess of sulfuric, nitric or hydrochloric acid, possible even in quite dilute solution. With acetic acid, however, the use of hydrogen peroxide does not produce this favorable result. ANALYTICAL LABORATORY, NATIOHALCARBONC O M P ~ H Y CLEVELAHD, OHIO ~
-
A METHOD FOR THE DETERMINATION OF ALCOHOL IN THE PRESENCE OF PHENOL' By J
EHRLICH
Received October 27, 1915
It has been repeatedly observed in this laboratory t h a t t h e usual method of determining alcohol in t h e presence of phenol by means of distillation from strongly alkaline solution is b y no means exact. Notwithstanding t h e presence of a large excess of alkali, a bromine test on t h e distillate invariably indicates t h a t a portion of the alkaline phenate always undergoes hydrolysis, allowin;: phenol ?a be carried over. InasinGch as tribromphenol or sodium tribromphenate would be expected t o have a much higher dissociation constant t h a n phenol or sodium phenate because of t h e brominated nucleus, it was thought t h a t t h e conversion of t h e latter into the former would result in decreased hydrolysis and hence obviate t h e difficulty referred t o above. The method proved t o be practicable. Aqueous solutions (8.6 and 2 0 . 0 per cent b y volume) of ethyl alcohol were prepared, a n accurately standardized bottle pycnometer being used for the determination of specific gravity. Throughout t h e work solutions were measured and t h e alcoholic distillates weighed a t 2 5 ' C. T h e j o cc. receiving flask and the 2 5 cc. and j o cc. pipettes mere found to be relatively correct a t 2 5 ' C. 1
Published by permission of the Secretary of Agriculture
