March, 1 9 2 i
IYDUSTRIAL A 3 D ENGINEERING CHEXISTRY
The moss contains considerable quantities of a wax. -4 concentrated hot benzene extract of the moss sets t o a gel on cooling. The wax is sparingly soluble in petroleum ether, but readily soluble in chloroform. An alcoholic extract of the wax isolated with benzene gave a distinct sterol reaction with digitonin. The petroleum ether extract of the moss was yellolv. On pouring this extract t'hrough a column of dry, precipitated calcium carbonate, there was obtained an upper preen ring (chlorophyl) and a lower pink one (carotinoid pigment). The n-ax deposited from all solvents as a gel. The best method of purification found consisted in pouring the chloroform solution into a hot solution of absolute metjhanol, in which the wax is sparingly soluble. The wax retained a greenish yellow color after repeated purification. The saponification number v a s 41.24. Saponification with alcoholic potash gare an alcohol melting a t 79-80' C. and solidifying :it 78-79" C. Ash
It will be noted that the moss is high in ash. TTherry and Buchanan'" consider the presence of silicon and iron a mystery. This is readily explainable in t'hat' practically all
411
the inorganic matter is derived from dust transported by the wind and rain, and caught by the leaf scales which are admirably adapted to this purpose. This view is supported by the fact that the entire moss contains 6.61 per cent of ash and the hair only 0.54 per cent. Summary
Spanish moss contains galactan, araban! xylan, and cellulose, and what appears t'o be a phenol methylether glucoside. Among the non-carbohydrate constituents are protein, chlorophyl, a carotinoid pigment, a sterol, and wax. Bibliography 1-Record, Sei. .I m . 1916, 2s. P--Billings, Botan. Guz., 38, 99 (1904) 3-Pickell, Florida Expt. Sta., Buil. 11 (18901; 12 ( l b 9 1 ) . 4-Luca, C o m p t . r e n d . , 53, 241 (1861). .j-Halligan, J . I n d . En!. Ciiem., 1, 206 (1909). 6-Baker and Pope, J . Chem. Soc. ( L o n d o n ) , 77, 699 (1900). i-Von Fel!enherg, Biochem. Z.,85, 68 (1916). 8-Farnell, I n t e u n . S U ~ W J . , 25, 248 (1923). 9-Clark, J , B i d . C k e m , 21, 645 (1919). lO--\Therry and Buchanan, .Science, 61, X I V (19251. 11-Marsden, C . S . P a t e n t 1,327,873 (1920).
Anhydrous Barium Perchlorate and Mixed AlkalineEarth Metal Perchlorates as Dehydrating Reagents' By G. Frederick Smith U R B A N AILL. ,
HE p r o n o u n c e d stability of the alkaline-
T
The increasing use of chemical reactions employing gases under pressure involves as well the need for their efficient dehydration. The qualities desirable in a drying agent f o r both commercial and experimental use have been Summarized. Chief of these desired properties are a high efficiency and capacity, possibility of preparation, and regeneration without fusion, modcrate Cost, and general applicability. The use-of a mixture of two dehydrating agents, each of which S U P plies desirable properties which are deficient in the other, has been shown to solve the difficulties in the Particular case of mixtures of anhydrous barium Perchlorate as the main constituent with anhydrous magnesium perchlorate as the minor component.
earth metal perchlorate, both a t comparatively elevated temperatures and in tile p r e s e n c e of reducing agents unsaturated hydrocarbons, carboil monoxide, and hydrogen, together Tvith their excessive deliquescence Jvhen in the anhydrous condition, iiiakes their use a j dehjrdrating reagents .i-ery attractiTe, both experiment,all\and industrially. A study of the preparation and propert,ies of magnesium perchlorate as the trihydrate and the anhydrous to determine their efficiency and capacity as drying agents, was made by TVillard and h more detailed etudy of the trihydrate of magnesium perchlorate and its use as a drying agent in steel and organic conibustio~~ analyses for carbon and hydrogen !vas carried out, by the >\*rite*alld collaborators.3 (This reagent is nom being distributed und1.r the trade llallle "Debdrite.") -1bibliography of the stlldy of the alkaline-earth metal as well as the alkali metal perchlorates up to a recent date has been previously publishetl.4 The present work consists in the demonstration of the Inany ad\-antages t o be deriT-ed from the use of variously prepared mixtures of anhydrous barium and magnesium perchlorates as desiccating materials. Received October 22, 1926. J . A m . Chem. Soc., 44, 2255 (1922). Smith, Brown, a n d Ross, THISJ O U R K A L , 16, 20 (1924). \T'illard and Smith, .I. .Am. Chem. Soc., 46, 286 (1923).
Requirements of a Drying Agent
The most important requirements to be fulfilled by a drying agent are as follows:
1-Its drying efficiency, or the degree of thoroughness with which it removes moisture from d i f f e r e n t g a s e s brought into contact with it, be very high. A list Of desiccating agents, t o g e t h e r with their classification as to dehydrating efficiency, has been reported by Baxter and collabor at or^.^ Phosphorus pento x i d e h a s b e e n shown by hhrley6 to be capable of d r r i w air, hydrogen, and oxygen t o such a high degree of efficiency, that the residual moisture in comparatively unlimited volumes of these gases after contact Jvith this desiccant is unweighable, Anhydrous magnesium perchlorate, as well as its trihydrate, has been demonstrated?z3 to be of efficiency equal to that of phosphorus pentoside a t moderate rates Of gas flow-. 2--The drying capacity, or the weight of moisture absorbed per unit weight of desiccating material, should be relatively high, For phosphorus pentoxide the drying capacity is very small. This is still more pronounced because of the physical characteristics of the reaction products formed. For other desiccants having higher drying capacity the well-spent reagent often acquires physical characteristics resulting in clogging of drying towers and tubes, original 3--It should be easy to restore the drying drying capacity and efficiency. Such regeneration would be much more satisfactory if it could be accomplished without 5 Baxter and Warren, J . A m . Chem. SOC.,33, 340 (1911); Starkweather, I b i d . , 38,2038 (1916). 6 Ibid., 86, 1171 (1904).
Baxter and
412
I X D USTRIAL A N D EWGINEERIiVG CHEMISTRY
removal of spent reagent from drying towers and tubes in which it is contained. 4-The reagent should be capable of preparation in granular form. This condition is necessary to afford minimum resistance to the flow of gases. A granular desiccant, to possess highest drying efficiency and capacity, must consist of highly porous individual particles. The granular condition of the reagent should be retained after regeneration. 5-The reagent should be stable and non-fusible at its dehydration temperature or above. Both conditions are necessary for the purposes of regeneration. The most efficient desiccant will require the highest temperature for its dehydration, and must therefore be stable a t such temperature. Drying agents fusing a t the dehydration temperature require graded sifting to separate granules from powder, a process which is wasteful and in other ways undesirable. 6-The desiccant should be rapid in its action. A very efficient drying agent may have desirable experimental value, but to be commercially suitable it must provide volumes of dried gases proportional to the requirements of the process with which the dried materials are associated. 7-The reagent should be serviceable in the drying of a large number of gases of widely different chemical properties. Phosphorus pentoxide, being an acid anhydride, would not be suitable for ammonia gas, but is reactive with many gases, the gaseous halogen acids, for example. 8-The drying material should be cheap. The cost of the material should be considered in relation to the first seven points, particularly the first three.
The mixtures chosen as the subject of this investigation possess the qualifications specified above.' Barium Perchlorate This material is most cheaply and conveniently prepared by the digestion of a nearly saturated ammonium perchlorate solution with hydrated barium hydroxide in 5 to 10 per cent excess of the theoretically required amount. Ammonia is given off as a by-product and by keeping the digesting solution a t the boiling point the reaction progresses rapidly to completion. As the ammonia is displaced and the barium perchlorate thus formed, the concentration of the solution may be allowed to increase, as a result of the high solubility, and temperature coefficient of solubility, of barium perchlorate. Fractional addition of the ammonium perchlorate facilitates the reaction and permits more concentrated solutions during digestion. After the complete displacement of ammonia from the solution the slight excess of barium hydroxide is neutralized with perchloric acid, which a t the same time dissolves the appreciable quantity of barium carbonate either contained in the barium hydroxide used or formed during the digestion by contact with atmospheric carbon dioxide. The solution of barium perchlorate thus obtained is filtered, concentrated if necessary, cooled, and crystallized. The solubility of barium perchlorate has been determined by Carlson* over the temperature range 0" to 140". One hundred cubic centimeters of water dissolve approximately 750 grams of the trihydrate of barium perchlorate a t 140" C. and approximately 200 grams a t 0" C. As a result of these solubilities crystals of any desired size are readily obtained and may be freed from the mother liquor by simple gravity drainage. Barium perchlorate trihydrate containing 13.85 per cent of water of crystallization, unlike the hydrated perchlorates of strontium, calcium, and magnesium, does not fuse in its own water of crystallization a t a temperature much in excess of that necessary for its complete dehydration. The dehydrated salt does not deliquesce in moist air beyond the trihydrate stage of hydration, Barium perchlorate tri7 Full patent protection for the processes and compositions employed in this description has been applied for. 8 Comey-Hahn, Dictionary of Solubilities, p. 649 (1921); Festk. Stockholm, p. 262 (1911).
Vol. 19, KO.3
hydrate, a t ordinary temperatures, over concentrated sulfuric acid is not dehydrated beyond the monohydrate stage. The trihydrate over anhydrous barium perchlorate forms the monohydrate. The last two facts indicate that anhydrous barium perchlorate is equal to or greater than concentrated sulfuric acid in dehydrating efficiency. Of all the metallic perchlorates except the alkali metal salts, barium perchlorate is the most stable. Long treatment a t 400" C. leaves it practically unchanged. Anhydrous barium perchlorate thus qualifies satisfactorily under most of the eight requirements of a successful dehydrating agent as follows: (I) efficiency equal that of concentrated sulfuric acid; ( 2 ) capacity roughly 14 per cent; (3, 4, and 5 ) capable of regeneration, granular, and very stable; (6, 7, and 8) satisfactory as to speed of dehydration (see Table I), inert, and a t the present market price of barium hydrate and ammonium perchlorate, even without ammonia as by-product, sufficiently cheap. Mixed Alkaline-Earth Metal Perchlorates a s Dehydrating Agents The properties of anhydrous barium perchlorate just enumerated indicate that its use as a carrier for a more efficient desiccant, such as anhydrous magnesium Perchlorate, would strengthen its weak points, such as its efficiency, capacity, and speed, without loss of its advantages. The infusibility of barium perchlorate trihydrate upon vacuum dehydration a t 100-140" C. may be considered to result from the high molecular weight of the anhydrous salt as compared with the trihydrate, together with its comparatively low dehydration temperature, both conditions preventing the material from dissolving in its own water of crystallization upon dehydration. The comparatively high dehydration temperature of magnesium perchlorate hexahydrate, which forms the trihydrate in oucuo a t 140-147' C. and the anhydrous salt only a t approximately 250" C., does not materially alter the infusibility of barium perchlorate trihydrate including mixtures containing 25 t o 35 per cent of the hexahydrated magnesium salt. As a result of these conditions, the state of granulation of a mixture of barium perchlorate trihydrate and magnesium perchlorate hexahydrate subsequent to dehydration a t 250" C. depends entirely upon the particle size of the first material prior to such treatment. The barium perchlorate trihydrate, upon treatment a t this comparatively high temperature, rapidly dehydrates completely, leaving a granular, porous medium for the absorption of the magnesium perchlorate hexahydrate which fuses a t a temperature less than 145" C. Upon continued treatment a t 250" C., the magnesium salt is completely dehydrated and the granular condition of the mixed reagents unchanged. The particular process of manufacturing the mixed drying agents may be varied quite materially without appreciably affecting the characteristics of the finished product. For example, in addition to the method of preparation described above, the granular barium salt may be dehydrated separately a t 100-140" C., followed by mixing with the desired amount of magnesium salt and dehydration to the anhydrous condition a t 250" C. Other methods might be employed and the resulting product possess a very satisfactory toughness of texture, which is favorable in causing the product to retain its original state of granulation. Mixtures of the magnesium salt with the barium reagent up t o 35 per cent of the magnesium salt give a product that does not more than sinter slightly upon dehydration. Fifty per cent of each component results in an unsatisfactory product. Eight hours a t 250" C. and 4 inches of mercury pressure is ample time to dehydrate such a mixture in trays with 10-mesh wire-cloth bottoms covered to a depth of
I S D C S T R I A L A N D ENGINEERI,\rG CHEMISTRY
RIarch, 1927
l,'2 t o 3/4 inches with '12-inch clearance between trays. A higher vacuum is desirable in speeding up the dehydration. A variation of 10 degrees in temperature is without material consequence.
M e c h a n i s m of Drying, Using Mixed Anhydrous B a r i u m a n d M a g n e s i u m Perchlorates
Consider a single particle of the mixed dehydrating agents a granular support or carrier of anhydrous barium perchlorate coinparable to a sponge partially saturated with anhydrous magnesium perchlorate uniformly throughout its structure. The mechanism of the drying action of such a single particle is then as follows: Upon contact with moist gases permeating the whole of each individual granule of material as the gases pass through a column of it, the molecules of anhydrous magnesium perchlorate absorb water to the hexahydrate condition, requiring 32.62 per cent of water of crystallization. At this stage of hydration the supporting material, anhydrous barium perchlorate, hydrates to the extent of three moleTable I-Tests
TEST 1 2 3 4 5 6 7
-
RATE
PER
Liters 68 68
so
55 53
36
55
413
was concerned with the regeneration of the spent reagent. I n each instance the drying efficiency was the same a t a given rate of gas flow, but in the second case the spent reagent became appreciably more moist a t the point of first contact and difficult to regenerate. I n the case of the 60 per cent saturation the spent granules of reagent never attained such a state of saturation as to result in the slightest tendency for the individual particles t o coalesce. Experimental Procedure The air to be dried was taken from the regular laboratory air-pressure line and passed through the saturator bottle and saturated solution of sodium bromide to establish GO per cent humidity and then passed directly into the reagent to be tested. The reagent was placed in drying tubes, either straight or of the U-tube type providing for columns of reagent 25 mm. (1 inch) in diameter and from 18 to 30 cm. (7 to 12 inches) in length. Glass wool plugs a t the exit end of the reagent tube provided a filtering medium for the dry gases emitted and permitted regeneration of the spent reagent tube. The dried air from the test reagent tube was passed into a second, much smaller, U-tube, containing alternate layers of purified ignited
of Drying Efficiency of Mixed Anhydrous Barium and Magnesium Perchlorates a t High Rates of Gas Flow and 60 Per Cent Saturation
TIME Hours 1
GAS
DRIED Liters 68
TEX-
c.
1 2 8 5.5
160 440 181
23 23 23.5 26 27.5
5.5 2
198 110
27 27.5
68
Mg(CIO4)s
DIXENSIONS OP
COLUMN
PERATURE
P e r cent 20.5 23.5 23.5 26.5 26.5 Ba(Cl0dr 100 100
WATER
ABSORBBD~
Inches 9x1 10 x 1 12 1 14 X 1 6x1
Grams 0.60
x x
2.17 1.16
x
12 12
1 1
0.61 1.86 5.70 3.32
WATER WATERUNUNABSORBEDA B S O R B E D Mg. 0.55 0.50 1.60 1.85 1.00 58.1
44.3
Mg. p e r lrter 0.008 0.007 0.010 0.004 0.004
0.29 0.42
~
a From t h e length of column of spent reagent the drying capacity of the 201.5,23.5, a n d 26.5 per cent magnesium perchlorate reagents was estimated t o be 30, 35, a n d 40 per cent by weight.
cules of water of crystallization, or 13.85 per cent, a t which stage it no longer absorbs additional water. Further contact between the moist gases and the mixed drying agents results in the hexahydrat'ed magnesium perchlorate further absorbing moisture. This account's for dehydrating capacities greater than the theoret'ical for any given mixture of these materials. The dehydration and regeneration of such spent granules result in a removal of water in the reverse order. For this purpose the evacuation and heating of the spent material should be carried out in such manner that the temperature is gradually raised to the point a t which the moisture in excess of that theoretically necessary in the formation of the true hydrates has been driven off. The regenerated material thus retains its original granular condition and drying tubes and towers can be used repeatedly nithout recharging. For an exact determination of the dehydrating efficiency of a given dehydrating agent, the partial vapor pressure of air retained in contact with such reagent until equilibrium is established should be ascertained. The procedure previously followed5 is applicable here. For the purpose of obtaining more serviceable data a different procedure mas employed dierein the gas rate of flow was greatly increased, using small-length columns of desiccant. This resulted in failure to obtain equilibrium conditions, but provided data concerning both speed and efficiency. A gas stream saturated with moisture was considered too severe a test to represent working conditions ordinarily encountered. The air dried in connection with the present investigation was passed through saturator bottles containing a saturated aqueous solution of sodium bromide, giving a gas 60 per cent saturated with water vapor. The only difference between the use of such a partial vapor pressure and that of a saturated gas a t the giren temperature
asbestos and 13-mm. (0.5-inch) layers of phosphorus pentoxide. The phosphorus pentoxide tube was protected against back flow of moisture by a second tube containing the same material. The temperatures of the drying agents and the gases dried were not controlled but were those of laboratory conditions, 25" C. or more. The gain in weight of the absorption tubes of test reagents was determined with an accuracy of a decigram. The weighed phosphorus pentoxide tube was counterpoised by a duplicate tube, a No. 10 Troemner balance and Bureau of Standards calibrated set of weights being employed. The weighings were made following determinations only after the tubes had been allowed to stand an adequate length of time on the balance pans and after both the weighed tubes and the counterpoise tube were momentarily opened prior to the final weighings. The rates of gas flow were determined a t the exit end of the gas train using the method of water displacement with timing by a stop watch. In nearly all experiments gas flow of from 50 to 80 liters per hour was maintained. Temperatures often reached 28" C. or over. The volume of gas passed was kept a t 70 to 400 liters. The rate of flow and the extreme avidity of the drying agent for moisture caused the drying tubes to become appreciably warm a t points in the tube nearest the admission of moist air.
The results of the tests, listed in Table I, show that for high rates of gas flow the most efficient reagent consists of 26.5 per cent anhydrous magnesium perchlorate, the remainder being anhydrous barium perchlorate. Test number 5 shows that even a column of drying agent 15 by 2.5 cm. (6 by 1 inches) is capable of drying air 60 per cent saturated with moisture passing a t the rate of approximately one liter per minute as efficiently as a column of the same reagent twice as long. This indicates that the longer column may be exhausted, through use, to the ext,ent of more than half its length before regeneration is required. This condition attests to the pronounced speed of absorption. (The speed of absorption is also evident from the regular advance of the spent reagent in the drying tube with no tendency to channel.) Tests numbers 2 and 3 demonstrate the slight de-
ISDUSTRIAL A S D ESGIAYEERINGCHEMISTRY
414
crease in efficiency with increase in gas flow-. Kumbers 6 and 7 show the tests of equal-length columns of pure anhydrous barium perchlorate as compared with the mixed reagent. The drying tube of experiment 5 was regenerated b y heating to 250" C. and evacuating to 102 mm. (4 inches) of mercury pressure and retested with no appreciable change in efficiency. The regenerated material had the same granulation after generation as before. It is probable that with higher percentages of the niagnesium salt the dehydrating efficiency of the resulting
VOl. 19, No. 3
material would be in excess of that found for the 26.5 per cent reagent investigated. This point was not tested because the cost of the preparation of these mixed anhydrous salts materially increases with increasing percentage of the magnesium salt. The reason for this condition becomes apparent from the details of the preparation of the magnesium salt.?s3 As a result of the possibility of drying the mixed perchlorate desiccating agent under vacuum and a t 250" C., the time of drying is greatly reduced and the cost is minimized. In all samples tested drying a t 250" C. and 102 mm. pressure during 8 hours was employed.
Solubility of Naphthalene in Certain Aromatic Hydrocarbons' By F. H. Rhodes and F. S. Eisenhauer CORNELL UNIVERSITY, ITHACA, N. Y.
crude light oil, crude acid oil, and naphthalene fraction and crude creosote oil. When these crude fractions are cooled some of the naphthalene may crystallize, rendering the oil turbid or even mushy or semisolid. Since the presence of solid material is objectionable in many of the products prepared from coal-tar oils, the refined oils from tar are often sold on a "limpid point" specification, which requires that the oil shall remain clear when cooled to a specified temperature. To give products of the required low limpid point, the processes for refining tar oils frequently include a cooling operation followed by filtration or whizzing to remove the excess naphthalene. I n the refining of tar oils it is frequently observed that the removal of the "tar acids" from the oil markedly raises the limpid point, and therefore it is commonly assumed that the cresols have an especially great solvent action for naphthalene. I n spite of the importance of the naphthalene content in determining the quality of tar oils and in affecting the refining operations necessary to give products of specified quality, there is but little available information as to the solubility of naphthalene in the coaltar hydrocarbons and as to the variation of the solubility with the temperature and with the concentration of tar acids in the oil. Preparation of Naphthalene and Solvents
The naphthalene used in this investigation was prepared b y the distillation of presumably pure naphthalene. The first and last portions were rejected, and only the middle fraction was collected for use. The redistilled material had a melting point of 79.9" C. and gave only a very pale yellow color when tested by the nitration test. The solvents used were toluene, xylene, refined heavy coke-oven naphtha, and a refined coal-tar oil which was prepared from creosote oil. The toluene and xylene were purified by washing with concentrated (93 per cent) sulfuric acid, 10 per cent sodium hydroxide solution, and water. The washed material 1
Received October 22, 1926.
heavy naphtha by a process s i m i l a r t o t h a t described above, except that the washing with sulfuric acid was repeated several times in order to remove all the unsaturated and polymerizable impurities. The refined tar oil was prepared from coal-tar creosote oil. The crude creosote oil was distilled and the fraction passing over between 230" and 310" C. was redistilled through an efficient column with heavy reflux to remove all of the naphthalene. The naphthalene-free oil was washed with 20 per cent sodium hydroxide solution and with 20 per cent sulfuric acid and was then again distilled t o remove water and tarry matter. The cresol used was from a special lot of material purchased as "pure meta-cresol" from a chemical supply house. It was free from oily impurities, and contained 94.2 per cent of meta-cresol as determined by the nitration test. The quinoline had a specific gravity of 1.091 and was free from hydrocarbons. It was dried over solid sodium hydroxide. Table I-Analyses DISTILLATION TOLUENE ~
~~
of Solvents C o ~ ~ T A CRESOL R
XYLENE
~~
Sp. gr. at 15.5' C. 0 . 8 6 2 Per cent c. Start 107.0 5 107.4 10 107.6 20 107.9 30 108.1 108.2 40 50 108.2 60 108.2 108.3 70 80 108.4 90 108.5 95 108.6 109.2 Dry Paraffins None
0.863
c.
131.0 136.0 136.2 136.4 136.5 136.6 136.7 136.8 136.8 137.0 137.2 137.4 137.8 None
0.864
1.030
c.
c.
154 157 158 160 160.5 162 164 166 168 171 176 177 188 o.2yo
239 244 246 248 249 251 254 257 261 267 279 290 303 O.e.70
0
1.042
c.
197.5 198.0 198.3 198.5
...
19a;5
...
19i:5 198.5 198.5 199.0
...
The analyses of the various solvents are shown in Table I. From the analyses it appears that the xylene was a mixture of meta- and para-xylene, practically free from the ortho isomer. The heavy naphtha was essentially a mixture of the various trimethyl benzenes. The coal-tar oil consisted
