December, 1931
I N D U S T R I A L A ND E N G I N E E R I N G C H E M I S T R Y
obtained by recovery from the same soil culture over a period of 1.5 years. The improvement in uniformity of yield, as well as yield per liter of medium, was great. The average weight of dry mycelium per liter of medium used was 23.1 granis. There v-as a maximum variation from this weight of 38 per cent, while the average variation was 11 per cent. Thus, for -4. s ~ d o i o ithe seed from soil cultures plainly gives superior re.sults. PREPAR-%TIOS O F S O I L STOCK C U L T U R E S
bstrate for mold stock cultures a. uyed in this r e r y simply prepared : To air-dried orchard loam soil (hfiami silt, loam) sufficient water is added to bring it to a moisture content of about 20 per cent,. The soil is then transferred in convenient amounts (about 5 grams on a dry basis) to ordinary half-inch (1.27-em.) culture tubes. The tubes are plugged Jvith cotton and given four 3-hour sterilizations at 15 pounds per square inch (1 kg. per sq. em.) pressure on alternate days, and tested for sterilit,y by addition of yenst-water-glucose broth to tubes selected at random. The tubes :%rethen inoculated with 1 cc. of a heavy spore or mycelium suspension of the desired mold and kept a t room temperature. That there is appreciable growth and sporulation on the soil can usually be ascertained without. difficulty by direct microscopic observation. While the addition of nutrient to the soil may bring about somewhat grwter growth, it does not seem t o enhance the keeping qunlities of th. cultures.
1299
It has been found possible to preserve on soil mold stocks used for large-scale gronth-namely, dspergillu,s fischeri, A. sydowi, and Penicillium chrysogenum-for over 2 years without loss of their essential and desirable characters. The results of testing such cultures of A. jscheri and A . syldowi are included under the soil averages in Table 1. Moreover, the gross colony characters have remained much more constant than did those of the corresponding cultures maintained in the usual way on agar slants. The soil cultures can be recovered as required simply by streaking some of the soil particles on fresh agar slants.. It is not in all cases advisable to depend on soil alone for the preservation of valuable stocks, but reserve stocks may without difficulty be prepared on soil, and the writers believe that in many instances soil will be found to be a n excellent medium for maintenance, with a minimum of change over long periods of time.
LITERATURE CITED (1) Barthel, C., Centr. Bakt., 11, 48, 340-9 (1918). (2) Peterson, W. H., Pruess, L. -M, Gorcica, H. J.. and Greene, H. C., ISD. EKG.CHEY.,25, 213 (1933).
RECEIVED August 11, 1934. This work !vas supported in part by a grant f r o m t h e Wisconsin klumni Reeearrh Foundation.
Saturated Solutions of Urea in Liquid Ammonia Vapor Pressures and Compositions from - 26.4" t o 101.0" C. WALTERSCHOLL AND R. 0. E. DAVIS, Fertilizer Investigations, Bureau of Chemistry and Soils, Washington, D. C.
U
REA is lrno~xmgenerally to in
The solubility of urea in liquid ammonia has ~ ~ ~~ ~ ~ ~ ~ ~ l $ ~ ~ been determined f o r the temperature range -26" or pressure gage and compressed ~ of the air for balnncing, 1 1 aid to 1010 C, The break in the solubilify curce mercury columns, the vapor presprobably indicates the transition f r o m co(ivH2)2.- sure of the material in A against YHS to CO(!VH2)2 U E 45.6" C. The solubility an air pressure. The volume of tube A and connection and the temperature-pressure curces indicate that to the mercury U is 6.09 cc. The is formed within the range of mercury manometer e m p l o y e d no was capable of measuring up to 5 temperature inzjestigated. The solubility deteratmo3pherea pressure. This will be minations trgree closely, in general, with those of A e?$!l& n(;t ~ ~ ~ h ~ a ~ ~ Junecke; there is a slight zariation for the s d u ing point of 132.7' C. vas used. bility near [he transition point, and at the higher S?.nthetiC ammonia was d r a ~ n
a n h y d r o u s liquid ammonia, but t'here have been no rneasurenlents of its solubility until recently. The only published data so far encountered are those by Jdnecke ( 2 ) in hi5 study of the carbon dioxideammonia-v-ater s y s t e m . The lnetllod enlployed b!, llilll is described in a n earlier paper ( I ) . New interest attaohes to solutions of urea in liquid ammonia temperature,s, since the successful operations of commercial processes for the synthesis of urea. Deternlinations of the solubility of llrea in anhydrous liquid ammonia over ,.he temperature range -26" t o 101" c. have been carried out by the authors employing a method whereby the solubility of the urea and the vapor pressure of t'he saturated solution are obtained in one apparatus.
SOLUBILITY DETERMIX'ATIOSS The apparatus employed is shown in Figure 1. The isoteniscope was constructed t o withstand pressures up t o 60 atmospheres. The Pyrex tube, A , 7 em. long, 9 mm. i. d., is soldered t o an inner cap and attached t,hrough a Rezistal valve, B , and tube to one arm of a U-shaped apparatus containing mercury. The two arms of the U are of capillary Pyrex tubing with 18 em. visible, incased in slotted steel cylinders and conuected a t the bottom with each other through a Rezist,al valve, L, .~PPARATUS.
from a cylinder, dried, and condensed by liquid air, and all noncondensable gases were p u m p e d off. Mixtures of the composition represented in Table I n-ere confined in chamber A of the isoteniscope. The required amount of urea was neighed and transferred t o this chamber, the vessel attached to the isoteriiscope, and the whole completely evacuated. The required amount of ammonia was measured in a volume buret and condensed into chamber A at liquid air temperature. The isoteniscope was placed in a water bath thermostatically controlled, The temperature mas adjusted to that temperature a t which all solid just passed into solution. The approximate temperature was first determined with similar mixtures in sealed glass tubes. The liquid mixture was continually agitated by a magnetically operated stirrer to prevent supersaturation. The heat from the magnetic coil surrounding chamber A was completely dissipated into the bath as found by actual measurements and did not affect the temperature of the mixture. The bath temperature was measured by a thermometer graduated in tenths of a degree and calibrated by t'he Bureau of Standards. -4fter establishing equilibrium by maintaining t'he mixture a t
I Y D U S T R I A L A X D E N G I K E E R I N G C H E M I S T R '5:
1300
VACUUM .+NO
iiR PRESZ,RE
A*NeLv-ca~ APPMATUS
AN0
-3-9
Vol. 26, KO. 12
The rewlts are given in Table I and are plotted on a weight per cent urea us. temperature graph (Figure 2 ) . An unbroken curve was not obtained probably because of the formation of a compound of the solvent with the solute. The breakin the curveat45.6"C. and 74.6 per cent urea probably corresponds to T7 the transition p o i n t of the compound CO% (NH?)S,NHI, w h i l e 8d l , l t h e p o r t i o n of the ! 1 3y ___ __ 2 -OL- -- - 1, curve below this point ' -I __ represents the solu2 bility of t h i s comgc3, 1 I . 5 1 1 pound in liquid amE 1 -' J,hHJ,CO monia. The portion 5 '' "3 , a b o v e t h e point is L i d representative of the ;, solubility of urea in E 301 CLLTE;hD-1 OETER'llhED VALUES liquidammonia. The JLV:CKf 5 \ 1 L d V curveisincloqeagreezoz 1 u__-ment with t h a t obrtained by Janecke ( 2 ) lo & L 4 5 20-EYWRATURE & 4 -OC butshoWs slightlTaria- FIGURE2. SOLUBILITY OF UREAI N tions near the break A ~ H Y D R O ULIQUID S AMMONIA and near 100' C. The break in the curve occurs a t what appears to be a n incongruent melting point which may be due to the inability of CO(I\;H2)rSH3to exist except in contact with solutions containing excess ammonia. The metastable continuation of the curve would reach the point representing the composition of 77.4 per cent urea (50 mole per cent) a t 46" C. The difference of 0.4' between Janecke's and the writers' values for the transition point is so small as probably to come within the experimental error. The break in the curve can be caused by either the formation of a compound of urea and ammonia, or by the difference in solubility of too crystalline forms of urea. Since only one crystalline form is known, the second alternative is rejected. The f o r m a t i o n of 4any other compound of u r e a a n d a m monia is not indil2cated on the curve. compound Of
7
I- -
zda-
'
~
L
FIGLRE1. I s O T E N I s C O P E EMPLOIED IU xTE4SLHI-G VAPORPRESSURES OF SATURATED SOLUTIOUS OF URE4 IN LIQUIDA m i o > ~ i the desired temperature for 4 hours, the total pressure of the solution was obtained by balancing the pressure through the U-shaped mercury manometer, K L J , and readings were made on a 5-atmosphere mercury manometer, or for higher pressures on a 200-pound test gage graduated in one-pound units. This gage was calibrated by the Bureau of Standards.
CALCULATIONS AND RESULTS From the volume and pressure of vapor of the solutions, the amount of ammonia in the vapor space of the isoteniscope was calculated. This quantity of ammonia subtracted from the total ammonia used in the mixture gave the actual amount of ammonia in the liquid phase. The possibility was recognized t h a t there may be some decomposition of urea a t the higher temperatures. Werner (3) describes the decomposition of urea as represented by the equation, (NHa)&O
=
NH,
+ HNCO
forming ammonia and cyanic acid. I n the presence of a n excess of ammonia, however, the likelihood of this reaction's taking place is diminished greatly. Assuming the formation of some cyanic acid, other possibilities are presented of the formation of ammonium cyanate, biuret, and cyanuric acid under these conditions. Because of the improbability of the formation of cyanic acid which would result in the presence of a complex mixture, the amount of urea found by analysis in the liquid phase after completion of the experiment was assumed to be the amount present in the saturated solution, and no correction was made for possible addition of ammonia to the mixture due to decomposition of urea.
'1
v-
__----I
~
D
~
5-
urea), but n o break is indicated in this
,
I
I
I
l
l
I
region. 20 ' 40 ' Sb 60 ,do Id0 T h e r e s u l t of TEMPERhTURT.. OC plotting the deterFIGLHE3. EQUILIBRIUM PRESSURE mined vapor p e a OVER A SATURATED SOLUTION OF sures in atmospheres U H E ~I N ANHYDROUSLIQUID AMof t h e m i x t u r e s MONI % TABLE I. COMPOSITIONS ASD 'APOR PRESSURES OF SATURATED SOLUTIONS OF URE IN LIQUID AMMONIA against temperature (NH*)?CO is shown in Figure 3. As the temperature rises, the solubility PER 100 O B S E R V ~ D increases and the effect of increase of temperature more than GR.AMS VAPOR TEMP, (NHz)zCO "3 NH3 UREA PRES SUR^ counteracts the depressing action due to increase of concenc. M o l e per cent Grams Wt. per cent Atm. tration of the compound CO(KH&.NH8,until the vapor pres-26.4 6.64 93.36 25.10 20.8 1.3 sure of the mixture reaches a maximum with rise of tempera5.8 15.26 84.74 63.52 38.8 4.7 23.9 23.39 76.61 107.6 51.8 7.6 ture and recedes thereafter to the transition point. Beyond 35.9 32.29 67.71 168.2 62.8 9.2 40.9 37.60 62.40 212.5 68.0 9.4 this point the vapor pressures again steadily increase with 44.7 43.59 56.41 272.5 73.2 9.0 concentration to a maximum of 13.6 atmospheres a t 90' C. 44.9 43.60 513.40 272.6 . 73.2 9.1 50.0 47.20 52.80 315.2 75.9 9.4 From this point the curve falls as the effect of increasing con61.8 52.05 47.95 382.9 79.3 11.1 81.0 61.39 38.61 13.4 560.6 84.8 centration on the vapor pressures is more pronounced and 82.0 61.53 38.47 563.9 85.0 13.5 would ultimately reach the vapor pressure of pure urea a t its 101.0 74.38 25.62 1024 91.1 12.5
December, 193 i
INDUSTILIAL A \ l )
E S G I S E E K I N G CHEMISTRY
melting qoint. JBnecke (2) measured the vapor pressure of urea c ' m e melting point and found it to be nearly one atm v 'iere.
1301
(3) IVerner, E. A . , "Chemistry of Urea," p. 24, LoIlgmans, Green & Co., London, 1923. RECEIVED September 22, 1934. Presented before t h e Division of Physical and Inorganic Chemistry a t the 88th Meeting of the .Imerican Chemical Society, Cleveland, Ohio, September 10 to 14, 1934.
LITERATURE CITED (1) Jtinecke, 2. Elektrochem., 35, 332 (1929). ( 2 ) .Jlinecke and Ernst, Ibid,,36, 636 (1930).
Action of Solvents on Coal Extraction of Edenborn Coal by Benzene at Elevated Temperatures R. S. ASBURY,Coal Research Laboratory, Carnegie Institute of Technology, Pittsburgh, Pa.
A study has been made of the ben:ene pressure extraction of Edenborn coal f r o m the Pittsburgh seam. Apparatus and methods are described f o r the pressure Soxhlet treatment of the coal, the determination of yields of soluble products, and their chemical separation. Reduction in particle size of the coal increases the yield of products. Increased yields result also f r o m heating ihe coal in presence of high pressures of benzene ziapor u p to 450' C. when combined with extraction at 260" C. The products resulting from benzene extracfion at 260' C. are largely neutral. with less than 3 per cent acidic, basic,
T
HE action of solvents on coal is of
both scientific and industrial iinportance. Their use offers a method of treatment whereby the coal structure may be simplified prior to a study of its c o m p o s i t i o n . T h e p o s s i b l e value of standard extraction tests in coal clawification has been indicated (4). It has been pointed out (12, 13) that,, in B study of Pthe mechanism of thermal decomposition of coal, solvent extraction offers probably the mildest type of pyrolysis. With the increasing importance of hydrogenation in research and industry, solvent action assumes a more prominent role, since hydrogenation is necessarily conducted in a dispersing medium. The importance of the effect of the dispersion agent on rate of coal hydrogenation has already been shown by Beuschlein and others ( 1 ) . I n spite of the recognized importance of the action of solvents on coal, relatively little attention has been given to a study of the nature of t h e e x t r a c t i o n process, which is dependent primarily on the nature of the solvent, time, t e m p e r a t u r e , and particle size for any given coal. Rate of heating and pressure are probably less important. I n v e s t i g a t o r s in the past have s t u d i e d a wide variety of coals with an equally wide variety of coal sizes, temperatures, times, and solvents. Unfortunately, therefore, direct c o m p a r i s o n of data is generally impossible. I n the work in this
and phenolic materials present. Combined eztraction and high-temperature heating result in increases in phenolic and basic materials, with increasing heating temperature and decreasing neutral ether-insoluble bodies indicating the possible formation of phenolic and basic materials from etherinsol ub les. W i t h benzene, under the most favorable conditions slightly less than 30 per cent by weight of ihe coal hus been made soluble. The curz'es of yield of soluble products vs. incerse time of extraction indicate thai complete dissolution of the coal would he impossible under these conditions. laboratory a n attempt is being made not only to study coal by extraction with solvents, but to use Edenborn coal as a means of studying solvent extraction. The work reported in this paper is concerned primarily with the factors of coal particle size, time, and temperature. For this study suitable apparatus has been constructed and studies have been made on the yield of extractable material with benzene with coal particle sizes ranging from 4 to 8 mesh to one micron, and also on the effect on yields of heating coal u p to 450" C. in the presence of benzene vapor.
APPARATUS The apparatus in which extractions were made was a specially designed p r e s ure Soxhlet extractor similar in principle to t h a t used by Bone ( 2 ) and constructed almost entirely of stainless steel (Figure l) : 9 closed system was used, making it possible to ext,ract in the liquid phase a t temperatures almost as high as the critical temperature of the solvent and permitting considerably higher temperatures for heat treatment of coal with solvent in the vapor phase. The steel shell, A , of the extractor was electrically heated, the temperature being controlled by a Leeds & Northrup recorder c o n t r o l l e r ( M i c r o m a x ) through an iron-constantan thermocouple in a steel well, A;, imbedded in the coal charge. Shell A was threaded into flange C and made gas-tight t o head B by a copper gasket. Steel -cup D held the fine-mesh wire basket or alundum FIGURE 1. DESIGX OF PRESSURE SOXHLET EXTRACTOR thimble as the size of coal required and was
