ALUMIh’A AS A S IOKIZIKG ADSORBEST* BY WILDER D. BANCROFT AND J. W. A C K E R X A S
The first part of this work was undertaken to verify the results of Weiser and Porter’ on the alizarin lakes. They claimed that the formation of hydrous aluminum oxide-alizarin lakes from sodium alizarate baths consisted in an exchange adsorption of the dye anion with the less strongly adsorbed chloride ion in the hydrous oxide and not to the direct adsorption of the neutral sodium alizarate as suggested by Bull and Adams? and by W l l i a m ~ o n . ~ The crystals of alizarin are a yellow orange color and in alcoholic solution have the same color, but the alkali and alkaline earth alizarates are dark purple. A thin film of sodium alizarate is purple in transmitted and reflected light, but the dilute solution possesses a red color. Since we found that alumina, prepared from amalgamated aluminum, treated with a sodium alizarate solution yielded a red lake, it seemed possible that we might have adsorption of the sodium alizarate.
Experimental Alumina from amalgamated aluminum. h pure alumina was prepared according to the outline given by hlellor4 by amalgamating a carefully cleaned sheet of aluminum with a few drops of a mercuric chloride solution, washing thoroughly to remove the chlorides, and allowing it to react with water. The oxide first formed was discarded because it was gray in color, and on further action a white, finely divided, oxide was formed. This oxide was tested for chloride by dissolving a portion in nitric acid and adding silver nitrate. No precipitate was formed, showing the absence of the chloride. The particles of the alumina settled out on standing, but a stable sol may be obtained by adding a small amount of hydrochloric acid in order to give the alumina sufficient positive charge to keep it in suspension. A saturated solution of alizarin was prepared from absolute alcohol. Also a solution of sodium alizarate was prepared by dissolving 2.88 g of Kahlbaum’s sublimed alizarin in the required amount of sodium hydroxide and diluting to one liter. Alumina and a l i z ~ r i n . While I O O cc. of alumina, prepared as above, was being stirred 5 cc of alizarin acid was added, and a pale pink coloration of the alumina was noted, indicating that little alizarin had been adsorbed. It * This work is done under the rogramme now being carried out a t Cornell University and supported in part by a grant prom the Heckscher Foundation for theAdvancement of Research established by August Heckscher at Cornell University. ‘Weiser and Porter: J. Phys. Chem., 31, 1824 (1927). J. Phys. Chem., 25, 660 (1921). J. Phys. Chem., 28, 891 (1924). J. W. Mellor: “Modern Inorganic Chemistry,” 774 (192j).
ALUMINA AS AN IONIZISG ADSORBENT
2569
was thought that perhaps not enough alizarin acid had been added. With the addition of I O cc more a yellowish brown precipitate was formed, which was not a true lake, for when examined under the microscope, silky crystals of alizarin were noted, which gave the lake the brown appearance Therefore, only a slight amount of the alizarin was adsorbed. To this mixture j cc of S / 2 0 sodium hydroxide was added and a red lake was formed. Also on another run j cc of concentrated ammonium hydroxide was added, and a red lake was formed. This lake was examined with a Bausch and Lomb chemical microscope equipped with an 8 mm objective, g j eyepiece and using transmitted axial light with daylight illumination. The sample was mounted in xylene because its index of refraction is near that of the alumina thus making the lake more transparent. A red color was homogeneous throughout the sample. These results are due to the insolubility of the alizarin acid in water. When the alizarin acid is added to the alumina, a small amount is adsorbed, but the rest is precipitated giving the crystals of alizarin and the brown color. V h e n the sodium or ammonium hydroxide is added, t8heinsoluble alizarin is converted into soluble sodium or ammonium alizarates respectively. The alizarin anion can now be adsorbed by the alumina, producing the red color. Following a suggestion of Professor Reiser of the Rice Institute the hydrous oxide was suspended in alcohol and treated with an alcoholic solution of alizarin. A red lake was formed, which was due to the adsorption of the alizarin anion. In this case the alizarin did not precipitate out, for it is soluble in the alcohol. A l u m i n a and sodzum alzzarate. Since the alumina adsorbed a small amount of alizarin producing a pink lake, an experiment was run to test the adsorption from a sodium alizarate solution. To I O O cc of the alumina, prepared as above, containing 0.251 g of A1203 sodium alizarate was added in varying amounts. The results are given in Table I.
TABLE I cc Na Alizarate
I 2
3
4 5
Observation
A pink lake with clear supernatant liquid. JJ ,, A light red lake ” A red lake with ” h red lake, slightly red Jl
JJ
?J
11
,I
t,
”
1)
1J
1,
I n this case we have a pure alumina adsorbing both ions, but the red color of the lake is due to the alizarate ion. Thus we may have direct adsorption of the sodium alizarate, although the cation does not influence the color. A l u m i n a gel and alizarin. An alumina gel was formed by adding 3 j cc of concentrated ammonium hydroxide to 12.5 g of Kahlbaum’s aluminum
WILDER D. BANCROFT ASD J. W. ACKERMAN
2570
chloride dissolved in 7 5 0 cc of water. The alumina, which settled out, was washed five times with distilled water, and part of it was peptized due to the removal of the coagulating ions. It was found, before, that the addition of the alizarin solution to the hydrous oxide precipitated alizarin due to its insolubility in water, and that only a small amount was adsorbed as the anion. Therefore, 7 5 cc of the gel was mixed thoroughly with 7 5 cc of alcohol and 20 cc of the solution of alizarin in alcohol mas added. Immediately a bright red lake was formed, which did not lose any of its color on washing. The filtrate gave a test for chloride, which indicated that in this case, the color was due to the alizarate anion in exchange adsorption with the chloride. A l u m i n a gel and sodium alizarate. 75 cc of the hydrous alumina gel was treated with 30 cc of the sodium alizarate solution and a bright red lake was formed. The test for sodium in the supernatant liquid showed that practically none had been adsorbed, since nearly all was present as sodium chloride. In this case we again have the exchange adsorption of the alizarate and chloride ions. These experiments check the work of Weiser and Porter' that the color of the alumina-alizarin lakes is due to the adsorption of the alizarate anion. More recently Weiser2 published another paper showing that the adsorption of the alizarin may be exchange adsorption, direct adsorption, or both, depending on the condition of the hydrous oxide. Our results are in accord with this view. Treatment of sodium alizarate with hydrogen peroxide. In connection with some other work on the fading of alizarin lakes, it was found that the color fade-ometer produced practically no effect. Grant and Elsenbast3 had faded dyes by means of hydrogen peroxide, which suggested the present treatment. The samples of sodium alizarate were treated with perhydrol as shown in Table I1 with the results indicated.
TABLE 11 cc N a .4liz.
cc Water
cc HIOz
Observations
(1)
5
IO
3
h red colloidal suspension
(2)
5
IO
4
(3)
5
IO
5
(4)
5
IO
(5)
5
IO
6 7
clearer than run (2) A red colloidal suspension An orange colloidal suspension h yellow colloidal suspension A yellow suspension, which settled out
Part of the suspension from run ( 5 ) was treated with sodium hydroxide and the purple color of the sodium alizarate was obtained. Weiser and Porter: J. Phys. Chem., 31, 1824 (192;). J. Phys. Chem., 33, 1 7 1 3 (1929). Grant and Elsenhast: J. Phys. Chem., 16, 546 ( 1 9 1 2 ) .
* Weiser:
ALUMISA AS AN IONIZING ADSORBENT
2571
These results could not be accounted for by a straight oxidation with hydrogen peroxide, for we have not only a change in color, but also a change in the physical properties of the solution to account for. However, there are acids present in the hydrogen peroxide, notably phosphoric, hydrochloric and sulphuric. On treatment of the sodium alizarate, the action is that of a strong acid on the salt of a weak acid, which results in the formation of the salt of the strong acid and liberates the weak acid, which is alizarin acid. Since it is insoluble, it precipitates. I n run ( I ) there was not enough acid present in the hydrogen peroxide to liberate all the alizarin acid so there is a suspension of the yellow particles, of alizarin or alizarin acid in the unattacked purple sodium alizarate, giving a red colloidal appearance. In run ( 3 ) there is more acid present and more conversion over to the alizarin acid and very little sodium alizarate left. Then in the last run there is complete precipitation of the insoluble alizarin acid. In regard to the action of acids on sodium alizarate Knechtl says: “Alizarin in sodium hydroxide yields a blue violet and in ammonia a purple color. It is precipitated from these solutions by hydrochloric and other acids.” We can then say that the action of the hydrogen peroxide is due to the acids present and not to the oxidizing power of the hydrogen peroxide. Treatment o j alizarin-alumina lakes with hydrogen peroxide. In each case 5 cc of the standard lake was used and treated with the amounts of the perhydro1 as indicated in Table 111. After the addition of the hydrogen peroxide the mixture was shaken for a few minutes and then allowed to stand for an hour and the results noted. TABLE I11 Run cc H202(30%). Observations I I S o change 2
3 4
3 5 6
5 6 7
,l t,
The lake was coagulated, and the red color was lighter. In all these runs the lake was coagulated, but the red color was left unchanged except a little lighter. In the last six runs yellow particles were noted suspended in the liquid.
8 9 IO
9,
1,
IO0
There was no change in the color or the condition of the lake up to the addition of 6 cc of hydrogen peroxide. None of the lakes lose the red color, although they are lightened a small amount. Apparently the acids have reacted with some of the sodium alizarate which was not adsorbed by the alumina and this accounts for the yellow particles in fine suspension. I n no case did the lake lose its red color. Any loss of color is due to an excess of sodium alizarate present which naturally gave the lake a darker color and Knerht, Rawson and Loewenthal: “A Manual of Dyeing,” 2, 573 (1910).
2572
WILDER D. BANCROFT A S D J. W. ACKERMAN
when the acids were added it was changed to alizarin. It was observed also that in the coagulated lakes the color was brighter which means that the alumina just adsorbed the correct amount of the alizarin anion and the remainder was converted to alizarin. This also bears out Weiser’s statement that an excess of sodium alizarate peptizes the alumina-alizarin lake. Then the lake will coagulate when the excess of sodium alizarate is destroyed. Hummell classifies the colouring matters as monogenetic or polygenetic. Monogenetic are such as are capable of yielding one colour, whatsoever mordant may have been used on the material, either before or during the dyeing operation. Magenta, indigo, and methyl green are examples of this class. Polygenetic colours are such as are capable of producing totally different colours according to the mordant employed. Examples of this class are alizarin, cochineal and logwood. Since we can obtain different colors with alizarin on various mordants, it must mean that t,he hydrous oxides adsorb the alizarin in a different manner. The alumina is colored red when treated with sodium alizarate, and also when treated with alizarin acid. In the latter case the red color is obtained if the alumina is suspended in alcohol so that the alizarin will not precipitate out when added to the suspension. This must mean that the alizarin is adsorbed in the ionized form. If alizarin gives different colors with various hydrous oxides used as mordants, what will the color be wit,h tin mordant‘? Knecht2makes the following statements about tin and tin mordants used witjh alizarin: “Sometimes a small amount of stannous chloride or bett’er stannous acetate is added to the mordanting bath to produce a more fiery shade: but what part the tin has in the formation of the color lake is unknown. Nothing definite can be said as to its mode of action. Moderately fast orange shades can be obtained with alizarin on cott,on mordanted with stannic oxide. The addition of a little stannous chloride to the bath renders the shade considerably brighter, but at the same time yellower. Alizarin produces with stannous chloride an orange shade on wool, fast to light, but affected by milling.” Apparently then the tin mordant must adsorb alizarin in a different manner than does the alumina. Preparation to the tin mordant. The hydrous oxide of tin was prepared by dissolving I O gms of stannous chloride in 240 cc of hot water and then adding 5.6 g of anhydrous sodium carbonate, The hydrous tin oxide was washed five times after its preparation. The sodium alizarate and alizarin solutions were used as previously prepared. Tin mordant and alizarin acid. Our previous experiments with alumina have shown that if we add an alcoholic solution of alizarin to the hydrous oxide as such, the insoluble alizarin precipitates. This was corrected by suspending the mordant in alcohol. ‘Hummel: “The Dyeing of Textile Fabrics,” 147 (1885). “A Manuel of Dyeing,” 2, 582, 598, 599, 600 (1910).
ALCMIKA AS A N IONIZlNG ADSORBEST
2573
On treatment of the mordant suspended in alcohol with a solution of alizarin in alcohol a yellow-orange lake was produced similar to the color of the alizarin. This indicated that the tin mordant took up the alizarin acid. Since the lake settles out on standing, it was filtered. The residue was washed five times with distilled water, but the color of the lake was unchanged and the filtrate \vas colorless. When treated with sodium hydroxide the color immediately changed to purple, and the lake was now washed again. The filtrate was a light red-blue color, but the greater part of the sodium alizarate remained adsorbed on the mordant. The residue was washed on t o another filter and the lake still remained purple and the filtrate clear, which showed that the hydrous tin oxide adsorbed sodium alizarate. 1t-e may rule out compound formation because it occurs neither with alizarin and hydrous alumina, nor with chromic oxide nor with hydrous iron oxide. Also as will be shoivn later we may have varying amounts of alizarin and sodium alizarate adsorbed on t'he mordant, which would not happen in compound formation. K e have txvo possibilities for the adsorption with alizarin acid, first that the alizarin acid is taken up by the mordant, and secondly that the hydrogen cation is adsorbed and drags on the anion with it. In either case the result is the same-an orange lake is produced. If the latter case were true we should have adsorption of the anion forming the red lake, but in no case do we obtain this. Tin mordant and sodium alizarale. The mordant, which was made slightly acid with hydrochloric acid was treated with the solution of sodium alizarate and a dark brown lake was produced. On washing, the color remained the same. Another sample was run using the same amounts of mordant and sodium alizarate but increasing the acid concentration. I n this case an orange lake was produced, and finally with more acid a yellow lake was formed. The explanation of this depends on the concentration of the acid. With large amounts of acid the sodium alizarate is converted into alizarin acid, which is adsorbed by the tin mordant. With decreasing concentrations of the acid the lake becomes successively darker which is due to the adsorption of some alizarin and some sodium alizarate giving a range of colors from yellow to purple. The latter is produced only if the mordant is on the alkaline side, for any acid present converts some sodium alizarate into alizarin acid, which makes the lake lighter due to its yellow color. The mordant was then made alkaline with sodium hydroxide and the sodium alizarate added. h deep purple lake resulted. The color was not lost on prolonged washing. These experiments show t'hat hydrous stannic oxide adsorbs alizarin acid, sodium alizarate or both, but does not adsorb the alizarate anion as such to give a red lake. The same experiments were done using a mordant prepared from stannic chloride and anhydrous sodium carbonate. The results were the same as noted above.
2574
WILDER D. BANCROFT A S D J. R '. ACKERMAN
From experiments previously conducted it appeared that hydrous zinc oside used as a mordant adsorbed sodium alizarate. The following experiments were perfornied to check this. Prepnrafion of the zinc mordant. To 40 g of zinc chloride dissolved in 7 5 0 cc of hot water at i o o C was added z j cc of concentrated ammonium hydroxide. The mordant x a s washed four times. I t was white and settled out on standing. 50 cc contained 0.9113 g weighed as anhydrous ZnO. Zinc m o d a n t a n d alizaTin acid. To I O cc of the hydrous zinc oxide made $lightly acid xith hydrochloric acid was added 5 cc of the alcoholic alizarin solution and immediately a yellow orange precipitate was formed. Since the mordant settled out it' could be washed, and most of the yellow color was washed out into the filtrate. A slight yellow color remained after repeated washings indicating a very small adsorption of the alizarin acid. This precipitate was treated with a drop of X sodium hydroxide and the lake turned purple indicating the adsorpt'ion of the sodium alizarate. This was washed repeatedly but the color of the lake remained the same, which was due to the adsorption of the sodium alizarate. To I O cc of the mordant made slightly alkaline with sodium hydroxide was added 5 cc of the alizarin solution and immediately a purple lake was formed. On washing, the filtrate was colored a lavender and the residue was purple, which showed that the sodium alizarate was adsorbed. Also it showed that the zinc mordant is not as strong an adsorbent as the alumina, for when the latter is used ad mordant' in the same amount and the alizarin acid the same the filtrate was colorless, and the mordant took up all the dye as the alizarin anion. Hydrous zinc oxide and s o d i u m alizarate. To I O cc of the mordant made slightly acid with hydrochloric acid was added 5 cc of sodium alizarate and the lake was colored purple, which on washing did not change in color but remained as a purple lake. However, the filtrate x a s slightly colored, which indicates that some of the sodium alizarate was not adsorbed. This was generally true in the experiments performed with zinc oside as mordant; it did not adsorb as well as the alumina or tin mordants. To I O cc of the zinc mordant made slightly alkaline with sodium hydroxide was added j cc of the sodium alizarate solution and the lake produced was purple, This was washed and although a slight amount came through into the filtrate the lake was still purple shaving the adsorption of the sodium alizarate. \Ye can conclude then that the zinc mordant when alkaline will adsorb sodium alizarate or alizarin acid which is converted into sodium alizarate by the alkali present, to give a purple lake. Also the mordant when acid nil1 adsorb sodium alizarate because the acid on the mordant is not enough to convert the sodium alizarate into sodium chloride and alizarin acid. As we should expect, in one case only do we fail to obtain the purple lake and this is when the mordant is acid and the alizarin acid is added. Since there is no
ALUMINA AS A N IONIZING ADSORBENT
2575
sodium present, no sodium alizarate is formed and therefore no purple lake is produced. From the experiments conducted we have found that alumina adsorbs the alizarate ion to produce the red lake, the hydrous tin oxide adsorbs alizarin acid, sodium nlizarate or both to form a series of lakes varying from yellow to purple, and the zinc mordant adsorbs sodium alizarate and alizarin acid (slightly) to give a purple lake in the first case and a very light yellow in the second. There are esamples of other substances which are adsorbed in different ways. Thus, IVitt’ notes that rhodamine does not fluoresce in the solid state, but does so in solution. Silk dyed with rhodamine showed plainly a fluoreecence. In other words, rhodamine is ionized in solution, and this produces the fluorescence. The silk adsorbs the ion giving the fluorescence, thus acting as an ionizing adsorbent. On the other hand wool dyed with rhodamine does not fluoresce, for Dreaper’?says: “Silk dyed wit’h rhodamine is fluorescent , wool is not.” Experiments were then undertaken using rhodamine dyed on wool, silk and cot,ton. Knecht3 gives t’he properties of rhodamine B as follows: “Rhodamine B is a red-brown or greenish crystalline powder; aqueous solution is magenta red with a brownish-yellow fluorescence. A light bluishpink is obtained on unmordanted cotton. K i t h wool and silk bright bluishpink shades are produced with a red fluorescence. “The aqueous solution of rhodamine 6 G gives a yellowish red with a strong greenish-yellow fluorescence. Pink or blue-pink shades are obtained with cotton. With silk, yellowish-pink shades with a very strong beautiful yellow fluorescence are obtained.” R h o d a m i n e B dyed on ti~ool,silk and cotton. The standard dye bath used in the esperiments contained 0 . 0 ; g of rhodamine B in 50 cc, and the samples of cloth weighed one half gram. The method of dyeing was to heat the bath to 40’ C, enter the cloth and raise the temperature to boiling, which was continued for one half hour. The samples were removed and dried in air. The fluorescence was tested by means of ultraviolet light. The source of this was a carbon arc, and the light was conducted through a focusing lens and then through an ultraviolet plate (Corning Glass Korks) which transmits only the ultraviolet light. If the materials are fluorescent they will emit light of a different color from that used to illuminate them. The results mere as follows: Rhodamine B does not fluoresce in the solid state, but does so in solution with 3 brownish-yellow fluorescence. On silk it yields a blue-red with a strong red fluorescence. On wool it yields a blue-red with a very slight red fluorescence. On cotton it gives a blue-pink with no fluorescence. Rlwduiiifne 6 C clyerl on zcool, silk oiicl cotton. These esperiments were rontluctcii in the same manner a s the rhodamine B esperiinents. ’ ,Jiilirl)ucli der Chemie, 1,
?
20
(1891).
Dreaper: “The Chemistry and Physics of Dyeing,” 170 (1906). Knecht: ,‘A Manuel of Dyeing,” 2 , 506 (1910).
2576
WILDER D. BANCROFT AND J . W '. ACKERMAN
The results were as follows: Rhodamine 6 G does not fluoresce in the solid state, but does so in aqueous solution with a green-yellow fluorescence. On silk it yields a yellowred color with a strong yellow fluorescence. On wool it gives a yellow-red color with practically no fluorescence. On cotton it produces a yellow-red color with no fluorescence. Experiments were then tried with the hydrous oxides and the rhodamine. (a). 2 cc of rhodamine B ( I g/liter) was added to jo cc of alumina, and a pink lake was formed. This was filtered and dried a t 60" C and then ground. On test for fluorescence a slight red-yellow fluorescence was exhibited. (b) 2 cc of rhodamine B was added to 54 cc of tin mordant, and a purple lake was formed. This was filtered, dried and ground. There was no fluorescence. (c). z cc of rhodamine B was added t o 40 cc of zinc mordant, and a pink lake was formed. This was a lit'tle darker than the alumina lake. I t showed a slight yellow fluorescence. (d) 2 cc of rhodamine B was added to j o cc of silica, and a pink lake was formed darker than the other previous ones. This gave a distinct yellow fluorescence, which was the brightest. The same experiments were carried out except rhodamine 6 G was used. TT7ith alumina there was a yellow fluorescence (slight). With tin, no fluorescence; with zinc a slight yellow fluorescence and with silica a distinct yellow fluorescence. Summary. ( I ) The tin lakes of rhodamine B and 6 G show no fluorescence. (2). The aluminum and zinc lakes of rhodamine B and 6 G show a slight yellow fluorescence. (3). The silica lakes of rhodamine B and 6 G exhibit a distinct yellow fluorescence. This must mean that in the presence of the silk and silica rhodamine is highly ionized and adsorbed. This produces the strong fluorescence. Since we believe the alumina acts as an ionizing adsorbent for the alizarin, it ought to be possible to show that it does so with some other substance. We chose violuric acid to work with after we found that alumina would not adsorb turmeric, paranitrophenol and phenolphthalein in either acid or basic color. V-ioluric Acid. The violuric acid obtained was a yellow pomder slightly soluble in hot water, yielding a violet solution. Wagner' says: "Magnaniniz has stated that violuric acid when dissolved in pure water is colourless, and that the colour of its salts in aqueous solution cannot be attributed to a coloured negative ion. His experiments were repeated but a colourless solution was not obtained; water carefully freed from alkali always giving a violet liquid. The absorption of solutions of the acid and the sodium salt is proportional to the number of violuric ions in the solution as determined by 1Z. physik. Chem., 12, 314 (1893). Z. physik. Chem., 12, 56 (1893).
ALUMINA AS AN IONIZIXG ADSORBENT
2577
electrical conductivity. The absorption of the acid does not increase proportionally to the dilution, as it should if the presence of a salt as impurity were the cause, but to the square root of the dilution. that is, proportionally to the number of negative ions. Sixteen solid violurates were examined. They show great differences in colour, but when dissolved in water and sufficiently diluted they all give violet solutions (due to the negative ion) provided the positive ion is colourless.” Donnan and Schneiderl performed a very carefully executed experiment which showed that a solution of violuric acid had a violet-red colour. Hantzsch’s view is that in an aqueous solution of violuric acid we have to deal with the equilibria, “Isomeric $ acid $ undissociated true acid F? ions. The equilibrium shifts towards the colourless (or nearly colourless) $ acid with falling temperature. The intensity of the aqueous solutions of violuric acid diminishes with decreasing temperature.” Hantzsch? describes as pseudo-acids those substances which do not contain a hydrogen atom directly displaceable by metals, but which are capable of changing into a salt-forming isomeride. The following tests may be used to recognize the existence of pseudo acids. ( I ) If an aqueous solution of a hydrogen compound neutralizes a base gradually, it is a pseudo-acid. ( 2 ) If a neutral or feebly acid hydrogen compound gives salts which are neutral or feebly basic, that is, are not) dissociated hydrolytically, it is a pseudo-acid, and the salts are derived from a more strongly acid isomeride. (3) i f a colourless hydrogen compound yields coloured salts and a coloured ion in solrition, it is a pseudo-acid. (4) Ah abnormally large positive temperature coefficient in the conductivity or the dis$ociation constant of a solution is an indication of a pseudo-acid. ( 5 ) If a hydrogen compound does not form a salt by direct combination with dry ammonia in a non-dissociating solvent, but does so in the presence of water, it is a pseudo-acid. (6) If a substance does not combine directly with water or alcohol, but yields a stable hydrate or alcoholate by indirect methods, it is a pseudo-acid. Violuric acid is colourless, but yields coloured salts and a coloured ion in solution, which makes it fall under classification (3). The same author3 notes that the sodium salt of violuric acid forms red needles, and the pot,assium salt crystallizes in bluish-violet needles. He claims that the alkali violurates exist in at least three differently colored forms, yellow, red and blue. As the atomic weight of the metal rises, the stability of the darkest colored modification increases. The yellow modification of the acid can only exist in the presence of lithium, the blue modification only in that of a metal of higher atomic weight. Also Hantzsch4 explains that the production of coloured salts from colourless acids and colourless metals must be accompanied by a constitutional J. Chem. Soc., 9 5 , 9 j 6 (19091. (1899). Hantzsch and Isherwood: Ber., 42, 966 (1909). Ber., 42, 966 (1909).
* Ber., 32, j j 5
2578
WILDER D. BASCROFT A S D J. W. ACKERMAN
rearrangement-an alteration of the manner in which the atoms are linked together. “With the salts of violuric acid, about one-half are carmine, whilst, the members of a smaller group coinprising the potassium, rubidium, and ammonium salts are bluish-violet to blue. The esistence of the colourless, yellow, red and blue isomerides may be explained by assuming that they are structural isomerides, having the following formulasI
-C’4
--c
--C’~S.OlZ (Yellow)
I :S.Oi\I
(Colourless)
I11
IV
--c (oal).o
--c,OM
11
-c:o
I
I
I
-c __ ?; Red)
II
--C.SO (Blue)
“The position of the metal depends on the nature of the solvent or catalyst which is present. When the solvent is renioved the metal may retain its new position or return t o its original one. This isomerism, which is due to change in linkage, and not to an alteration in the relative position of the atoms in the molecules is termed allodesmism.” The violet solution of violuric acid was treated with sodium hydroxide and B red color was produced. Another sample was treated with potassium hydroxide and a blue-red color was formed. A l u m i n a and violuric acid. Ten grams of violuric acid (Eastman) were dissolved in zoo cc of boiling water, and the color of the solution was violet. I O cc of this solution was added cold to 5 cc of alumina, and a violet lake wa6 produced. This was washed with water and most of the color went into the filtrate, but the alumina was still left a violet color after repeated washings, indicating the adsorption of the violurate ion. \Then treated with dilute hydrochloric acid the color was not affected. With concentrated acid, i t was changed to colorless because the anion of the acid displaces the violurate ion. I O cc of t,he violuric acid solution was treated until colorless with a solution of 0.1S hydrochloric acid, and it required 0.2 j cc. The violuric acid was now added to j cc of alumina, and a violet lake was formed comparable to the lake formed above. This was washed and the color remained violet. Also the color of the lake was not changed by the addition of dilute hydrochloric acid. Again this shows that the alumina adsorbs the violurate ion, although slightly as compared with alumina and alizarin. A l u m i n a and sodium aiolurate. Five grams of violuric acid were dissolved in 100 cc of boiling water and to this was added 2 0 cc of a sodium hydroxide solution (6 gms/zoo cc). The color of the sodium violurate is red as indicated by the porous plate test and evaporat,ion to dryness. In the concentrated solutions the color is red by transmitted light, but in dilute solutions it is a violet color. I O cc of sodium violurate was added to I O cc of alumina, and a red lake was formed. When washed the red color went into the filtrate, and the lake was violet, showing the adsorption of the violurate ion and not sodium
ALUIMISA AS AN IONIZING ADSORBEST
2579
violurate. When I O cc of the dilute solution was added to I O cc of the alumina, a violet lake v a s formed, which lost some of its color on washing but remained violet. Therefore, we may say that alumina adsorbs the colored violurate anion producing a violet lake. T Z I mordant L and violurzc acid. Since the tin mordant adsorbed the alizarin acid giving it a yellow-orange color, it may adsorb the violuric acid yielding a colorless lake. The tin mordant prepared as previously indicated and to which a small amount of sodium hydroxide was added to bring it on the alkaline side, was treated with violuric acid. There was a violet-purple lake formed, which was washed thoroughly with water. All the color went into the filtrate, leaving the mordant. On addition of a little more sodium hydroxie a purple lake was produced. When this was washed, the color went into the filtrate. This shows that the hydrous tin mordant will adsorb a slight amount of the colorless violuric acid, but it does not adsorb the anion to form a colored lake. Then the tin mordant was made slightly acid with hydrochloric acid and violuric acid added in varying amounts. Xo colored lake was produced. The mordant was washed thoroughly with water. If colorless violuric acid is adsorbed, treatment with sodium hydroxide should yield a color due to the liberaticin of the anion. KO color was formed, which showed that under these conditions the tin mordant did not adsorb violuric acid. Tzn mordant a n d sodium oiolurate. The mordant was again made alkaline and treated with the red solution of sodium violurate. There was a red-blue lake formed, but when mashed the color went into the flltrate leaving a colorless residue. This was treated with sodium hydroxide to determine if any violuric acid had been adsorbed. There was no color formed, showing there was no adsorption of violuric acid nor of sodium violurate. The mordant was made acid and treated with sodium violurate. The color of the lake was red-blue, but when washed the color went into the filtrate, leaving the colorless mordant. Thus we can say that the hydrous oxide of tin does adsorb sodium violurate. The same experiments were tried with hydrous zinc oxide as mordant, and it was found that there was no adsorption of the violuric acid or sodium violurate. Summary I. An alcoholic solution of alizarin added to alumina gives a pink lake, indicating the slight adsorption of the red anion. Further addition precipitates out the alizarin, since it is insoluble in water. 2. If alumina is suspended in alcohol, and then treated with an alcoholic solution of alizarin, a red lake is produced. 3 . Sodium alizarate added to alumina gives a red lake, but the color of the lake is unaffected by the nature of the cation.
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WILDER D. BANCROFT A S D J. W. ACKERYAN
4. The results 1-3 confirm the work of Weiser on the alumina-alizarin lakes, that the adsorbed alizarin is ionized. j. Sodium alizarate treated with hydrogen peroxide changes its color due to the acids present and not to an oxidation. 6. Alumina-alizarin lakes coagulate and become lighter on treatment with perhydrol due t o the reaction of the acids present with unadsorbed sodium alizarate. 7 . The hydrous oxide of tin adsorbs undissociated alizarin to produce an orange lake, and undissociated sodium alizarate to yield a purple lake, but does not adsorb the alizarate anion to give a red lake. 8. Zinc mordant adsorbs undissociated sodium alizarate to produce a purple lake. 9. Silk dyed with rhodamine B is blue-red with a strong red fluorescence, wool is blue-red with a very slight red fluorescence, and cotton is blue-pink with no fluoresecence. IO. Silk dyed a i t h rhodamine 6 G is yellow-red with a strong yellow fluorescence, and on wool and cotton is yellow-red with no fluorescence. 1 1 . The tin lakes of rhodamine B and 6 G show no fluorescence, the alumina and zinc lakes show a slight yellow fluorescence, but the silica lakes exhibit a distinct yellow fluorescence. 12. In the presence of silk and silica, rhodamine is highly ionized and adsorbed, which produces the strong fluorescence. Alumina, zinc, tin, wool and cotton exhibit practically no fluorescence with rhodamine, which must mean that it is not adsorbed the same in these cases as on the silica and silk. 13. A light violet lake is formed with alumina and a solution of violuric acid, but the adsorption is slight. 14. Hydrous tin oxide adsorbs violuric acid slightly but no color is produced, and therefore it is the undissociated acid which is adsorbed. Tin oxide will not adsorb the colored ion to yield a colored lake, nor sodium violurate t o give a red lake. 15. Hydrous zinc oxide adsorbs neither violuric acid nor sodium violurate. 16. Witt’s theory of solid solutions in dyeing loses its only support as soon as one postulates an ionizing adsorption.
Cornell I-nwersaly
