I
DONALD F. OTHMER, Polytechnic Institute of Brooklyn, Brooklyn 1, N. Y. KlCHlRO KON and TAKE0 IGARASHI, Shin Nippon Chisso Hiryo K.K, Tokyo, Japan
Acetaldehyde by the Chisso Process b b b b
Uses hydration heat for rectifying acetaldehyde Eliminates recycling of acetylene and produces higher yields Has low mechanical and operating l0SSeS of acetylene Requires a simple and relatively inexpensive plant
l V l O S T of the tremendous quantity of acetaldehyde produced throughout the world never reaches the market as such, but is used in the production of acetic acid and its derivatives. This acetaldehyde is largely produced by the catalytic hydration of acetylene in the presence of mercury salts and sulfuric acid in plants in Germany, Canada, the United States, and elsewhere. These developments have been reviewed by Kirk and Othmer (3), Shenvood (6),Ullmann (S), and others. The volume of material produced makes it important to study processing methods, 80 as to increase efficiency of the conversion and recovery, reduce the heat and power required, and simplify equipment and processing. Studies have therefore been made on the physical and chemical effects in the reactor, the design of the reactor, and the redesign of processing to simplify and make the process more economical. Plant data
. 2.
rigure
Present or German Process Acetaldehyde is usually made from acetylene by the hydration of acetylene (the German process), which in substance is used in many other countries besides Germany. It is operated usually in the following steps and equipment: 1. The hydration of acetylene is conducted in a reactor or absorbing tower in the presence of an acid solution containing catalysts, such as mercuric salt, and manganese dioxide or ferrous and ferric salts. A large excess of gaseous acetylene is used to sweep out to coolers the acetaldehyde produced along with water vapor. This reactor may be any suitable gas absorption tower; it is usually an injection tower which contains catalyst solution and has a foam separator on the top.
8. Find rsctifior
Rsctiftacfarcrvderolvti~n
9, 10,l 1,12, 13. Coolen 14. Heat eichonger 15. 16. Condeniers
I N W R M A L AND ENOINEEUNO CHEMISTRY
,
2. The cooling, condensation, and absorption of the acetaldehyde and of the excess acetylene and water vapor are done in a group of coolers and a water scrubbing tower. 3. The weak solution of acetaldehyde and acetylene in cooled water is rectified in a fractional distillation system to give a product containing 99% or more of acetaldehyde. This is usually carried out a t atmospheric pressure; and all or a major part ofthe heat which is supplied by steam at the reboiler of the rectifier is removed in the condenser a t the head of the column by artificially refrigerated water or brine. Some plants however, have adopted a rectification at high pressure to raise the condensation temperature of acetaldehyde sufficiently high so that cooling water of normal temperature may be used. 4. The'scrubbed gases leaving the main acetaldehyde recovery absorber re recycled to the hydration tower. In
Flowsheet of German process for acetaldehyde .p&duciion
Reactor
3,4, 5. Pump* :6 Rediflsr
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.
from several reactors of two different types were used in correlating the calculations from laboratory data.
18. Aldehyde w o h r lank 19, 20. Crolonoldahyde. '
rectifier,
21. Scrubber of purge gas
'
23. High pressure worher 24, 25; S e p ~ r d o n 26, 27. Redvcing tanks 28. Exponrion valve
some modern plants about 20% of the gas, which contains residual acetaldehyde, is compressed and scrubbed again with water, before recycling; in older plants this was done at atmospheric pressure by a low temperature scrubbing. Many interrelated pieces of equipment are ordinarily used for this simply described process; a flowsheet of a typical plant is shown in Figure 1. Table I gives representative figures on materials and energy required. I n this process, a large excess of acetylene is cycled through the reactor, which operates at a temperature known to be higher than desirable. The reaction heat of the hydration of acetylene is wasted by the cooling in the several cwlers and the scrubbing tower. A large amount of additional heat is required to heat the distillation column; and usually, artificial cwling is required to remove this heat at the top.
CHEMICAL PROCESSES
Chirro Process A combination of vacuum and pressure operations makes possible the reaction a t a lower tempdrature and without excess acetyleoe, and the separation of the acetaldehyde without the uee of steam for heating or refrigeration for condensing or absorption below usual cwling water temperature. This new method (the Chisso process) has been operated in single units with capacities u p to 30 tons per day by the Shin Nippon Chisso Hiryo K.K. for the past 5 years. The distillation temperature of the acetaldehyde from the acid catalyst is lowered; and subsequently the uncondensed vapors are compressed to a sufficiently high pressure to allow the condensation of acetaldehyde by cooling water at usual temperature. A compressor is thus used between the still itself and the rectifying column that separates the vapors. The plant equipment required for the Chisso process consists of an acetylene absorbing tower or reactor, a vacuum still, a partial condenser for the water in the vapors leaving the reactor, a compressor operating normally at subatmospheric preasure on the suction side and
Table 1.
Acetylene (or caIcium carbide MCrCUrY Sulfuric acid (100%) Nitric acid Ferric sulfate Eldtrie power Steam Operating labor 130,000,000 Ib./yr. plant 45,000,000 lb./yr. plant 20,000,000 lh./yr. plant
Acevlene feed line Absorption tower lreoctor) DId“ Pvrge gar scrubber Purge pipe for inen gases
U
-
6. Water of make-up solution 1 1 .
Inlet
12.
7. 8.
13. 14.
Pump Flash evaporator 9. Partial condenser
.^
..I
superatmospheric pressure on the deliver side, and a rectifying or fractional distilling column. Considerable simplification of the pmduction flowsheet is thus possible, as shown in Figure 2. Acetylene is fed to the reactor, where the desired chemical reaction is accomplished at from 68°t0730C.andabout1050t01100mm. ofmercury pressure. The feed acetylene is completely hydrated with water in the single operation. An acetylene scrubber is superimposed on the reactor. A purge pipe vents nonreacted gas such as nitrogen or other fixed gas. At the head of the scrubber may be introduced catalyst, such as a mercuric sa’t and manganese dioxide or ferrous sulfate, with fresh acid solution. The acid solution containing catalyst, so-called “mother liquid,” is passed to a
Requirements for Acetaldehyde Production G n m n Proccrs Chmo Proccrr, Pn w t n c ton Per 7OWpounds per Mcfnr Ton oretddthydd (8) 600 CU. mcten 2 tons) 0.7 kg. 5 4 kg. 6-7 kg. 5-7 kg. 100 kw.-hr. 3000 kg.
orclnldahydc ( 6 ) 630 pounds
Accloldehydc 560 CU. meters
1 pound 5 to 10 pounds
0.6-1 kg. 25 kg.
4 to 9 pounds 40 to EO kw.-hr. 3700 pqunds
245 kw.-hr. 200 kg.
1.2 man-hours 2.8 man-hours
2.6 man-hours
IS.
.
Campressr Rectifying tower Weter bonomr
Condenser Acetaldehyde receivw
vacuum still. The components of this mother liquid change with variations in the operating conditions, and usually consist of about 20 to 25% sulfuric acid, 1.5 to 2% acetaldehyde, 0.15 to 02yc mercury as metallic mercury, and 2 to 4% total iron as metallic imn. The vacunm flash still operates at a temperature lower than the hydration temperature of the reactor. The operating pressure and vapor composition are changed with the condition of mother liquid, and the pressure is usually about 225 mm. of mercury; and the vapors overhead contain about 70% acetaldehyde by weight. The vacuum still has no external source of heat and may be regarded as a simple flash chamber wherein the hot mother liquid carrying acetaldehyde is flashed at the lower pressure maintained there. Acetaldehyde is thus vaporized by conversion of the sensible heat (acquired thmugh the hydration reaction) to the latent heat of the vapor of water and acetaldehydc. The mother liquor, having lost about 60% of its total acetaldehyde content, paases back to the top of the reactor at a temperature within about 5’ C. of that in thereactor. Mixed vapom from the vacuum still have some of the water partially condensed in a fractional partial condensing tower with reflux condenser, until the vapor temperature is lowered to about 35O C. The acetaldehyde content in the vapor is increased to about 86 weight %. This fractional condensation is an evident rectification due to the VOL. 48. NO.
I
AUQUIT 1956
1259
large latent heat of water, even though there is no reboiling a t the bottom of the tower. Acetic acid and other products of high boiling point are taken off a t this tower bottom in a n amount ordinarily less than 1% of the produced acetaldehyde. This drain may also include a considerable quantity of metallic mercury which has been reduced and is thus recovered for re-use. Vapor leaving the top of the condensing tower is compressed by a turbocompressor up to 2.5 atm. At this pressure, the condensing point of pure acetaldehyde is 43" C. These vapors are fed into a final rectifying column. A small quantity of crotonaldehyde and accompanying water is drawn out at the bottom of this column. At the final overhead cooler of the reactifier, pure acetaldehyde is the product. 411 vents are connected to the suction through a water seal. or similar device; and waste gases are purged through the reactor and vent scrubber on the top, in order to recover any acetylene that may be contained or dissolved in acetaldehyde and water.
Features of Chisso Process The Chisso process has the following good features: I t eliminates the disadvantages of recycling excess acetylene. The reaction has less unfavorable side reactions and hence higher yields, due to the low reaction temperature. The reaction heat is removed and reused by a combination of vacuum evaporation and high pressure rectification. h-o refrigeration is required in the manufacturing operations ; and cooling water of relatively high temperature may be used in all coolers and condensers. The mechanical and operating losses of acetylene are low, owing to the simple process flowsheet, lack of recycling, and the few units. The plant is simple and relatively inexpensive. I t also has some possible disadvantages. The process has a lower reaction velocity of hydration, owing to its low temperature and the lack of a large excess of acetylene. This requires a larger hydration tower; however, this is a relatively inexpensive piece of equipment. The operating conditions for the turboblower used as a compressor for the aldehyde vapor are severe. There were some problems in mechanical design and construction materials to withstand corrosion and erosion, but these have been solved in the several years of operation. Utilization of Reaction Heat in Distillation. The best feature of the Chisso process, aside from high yields, may be the advantageous use of hydration heat for rectification of the acetaldehyde produced. The heat of reaction given off in the reaction of acetylene with water is large, and the amount of heat created by the reaction to produce 1 metric ton of acetaldehyde is enough to evaporate all
1260
of the acetaldehyde produced, and in addition about 1.2 metric tons of water. CzHz(gas)
+ HzO(liq.)-+CH&HO(liq.) + 33.7 kcal. per gram-mole
Reaction heat per 1 metric ton of acetaldehyde 33.7 kcal. per gram-mole X 1000 X 1000 gram-mole per kg. 44 = 766,000 kcal. per ton = 766 kcal. per kg. =
~
The latent heat of vaporization of the two components a t their respective boiling points is Acetaldehyde 137 kcal. per kg. at 20.8" C. Water 540 kcal. per kg. at 100' C. The heat remaining after the produced aldehyde evaporates is 766 - 137 = 629 kcal. per kg. of CH3CH0 This heat is enough to evaporate the following quantity of water: 629/540 = 1.16 kg. per kg. of CH,CHO While this figure will change according to the evaporation conditions, the quantity of water that can be evaporated may be about 1 to 1.2 tons per ton of acetaldehyde produced. Furthermore, a binary mixture of acetaldehyde and water is readily separable into the pure components by rectification. The high reaction heat of hydration and the wide spread of vapor and liquid equilibrium compositions make it possible to combine reaction and high pressure rectification by a utilization of the reaction heat. This requires the careful selection and maintenance of the reaction pressure, the flash separation pressure, and the distillation temperature. This control of pressures is possible through the use of a compressor which compresses from the partial vacuum of the acetaldehyde separation from the mother liquor to the high pressure of the rectifying column. This gives a higher pressure for the final condensation of acetaldehyde, so that cooling water of the usual temperature may be used. Thus. the vapor of acetaldehyde and water which is evaporated in the vacuum still carries the reaction heat of hydration to the rectifying column. as latent heat of evaporation. This heat, together with the heat of compression, is then used as the source of reboiling heat a t the base; and it is sufficient in quantity, as the rectification of acetaldehyde needs only a small reflux ratio because of the wide spread of vapor and liquid composition. This correct selection of the temperatures of reaction, flash separation, and distillation in the rectifier results in a considerable saving in electric power as compared with that required for a refrigerator, as the horsepower consumed in the operation of the compressor is much less than that required for the mechanical refrigeration of the cooling water. Both power consumptions increase with in-
INDUSTRIAL AND ENGINEERING CHEMISTRY
creased temperature of the availablc cooling water; but power consumption for the refrigeration increases much more. Of more importance may be the large saving of steam as compared with processes that also operate the distillation at a substantially superatmospheric pressure, but require heat in the evaporators and stills. Low Temperature of Reaction. A second feature of the Chisso process is its reaction system, which utilizes a low temperature-with corresponding low losses due to side reactions-and no excess acetylene. Other modern processes hydrate acetylene in a mother liquid of a relatively higher temperature; the aldehyde produced is swept out of the mother liquor with a large excess of acetylene as quickly as it is formed. This is to avoid any considerable resin formation or other unfavorable side reaction due to the high temperature. However, the excess acetylene may cause large mechanical losses of acetylene and a rapid inactivation of the catalyst. On the other hand, the high temperature of the reaction gives a more rapid hydration reaction than in the Chisso process. The hydration reaction may be considered from the standpoints of reaction velocity, side reactions, and life of catalyst.
Theoretical and Experimental Studies As in many other cases, the rate oi' hydration of acetylene is a composite ol the physical functions taking piacc within the film (diffusion of gas into the liquid), and the chemical reaction within the liquid. The kinetics of the reaction have becn studied (7-3, 7). Ueno and Orido (7) gave an excellent analysis, resulting in an equation showing the rate of hydration of acetylene. O n the basis of a theoretical analysis and some simplifying assumptions, this may be combined with the diffusional factors to give an over-all rate of removal of acetylene: d L' & -
c,~1 _1_ _ _ 1
mo+m
The values of k , were determined i n experiments to be reported elseivherc, and plotted by the method of Othmer and Luley (4) as in Figure 3 to givc straight lines. The slopes of these lines allow the determination of the heat of formation of acetaldehyde from acetylene (4). The tangent of the line for 20% sulfuric acid is 2.15, which, when multiplied by the latent heat of 1 mole or water at 70" C., gives 21,700calories per mole or 21.7 kcal. per gram-mole of acetylene. The large slope of the lines in Figure 3 shows that k, has a high coefficient with temperature; the value of k , is approximately tripled by a IO" C. elevation in temperature.
CHEMICAL PROCESSES Substituting these values in the above equation yields dV
=
760 cu. meters per hour of acetylene, at S.T.P. for the German process
dV and- = 282 cu. meters per hour of dt acetylene, at S.T.P. for the Chisso process
4'
c
M p o r Pressure of Waler
(mm)
Figure 3. Reaction velocity as a logarithmic function of temperature and acid concentration
A careful study was made of the solubility of acetylene in sulfuric acid solutions of various strengths. These data will be reported elsewhere. They influence the diffusivity coefficient, which is important, because it controls the rate of solution of acetylene from the gas phase into the liquid phase. The diffusivity coefficient may be determined at any temperature by the method of Othmer and Thakar (5) if it is known at two temperatures. The over-all rate equation with values of rate of chemical reaction and rate of physical diffusion may be used for designing the reaction tower. The data in Table I1 have thus been obtained, following some necessary assumptions for both the German type process and the Chisso process.
or, on the basis of 509 cubic meters of acetylene per ton of acetaldehyde, acetaldehyde production in tons per day is 35.8 for the German process reactor and 13.3 for the Chisso process reactor. These calculations afford an interesting comparison between theory and practice, although they cannot be regarded as exact, because of the assumptions involved. O n the basis of these calculations, a larger plant using the Chisso process has been designed for a production of 30 to 40 tons per day. The tower has a greater diameter (1.8 meters) and a greater rate of recirculation. Its performance is well within the expected range, as shown in Table 111. When these results are compared, it is seen that the velocity of absorption is greater in the German process than in the Chisso process. In practice, this means merely that the reactor alone, a relatively simple unit, will have to be larger in a plant using the Chisso process.
Side Reactions and life of Catalyst A low temperature for the operation of the absorbing reaction, such as is used in the Chisso process, has some advantages. One advantage is a high content of acetaldehyde which may be obtained in the mother liquor, owing to greater solubility. The acetaldehyde content
4
Table II. Data on German and Chisso Processes Plant Data German Process Chisso Process
Dimensions of reactor Diameter, meters Height, meters Cross-sectional area, sq. meters Reaction temp., C. Reaction pressure, atm. Acetylene feed, cu. meters/hr. at S.T.P. Components of mother liquid HzS04, % HgO,,g./100 cc.
Production, metric tons acetaldehyde/day Calculated Data DL,sq. cm./min. X IO3 d , cm. K , cm./rnin. C, 100 cc./(g.) (min.) V I , cc. x 10-6 S, calcd., with assumptions of size and rate of diminution of bubbles, sq. cm.
1
10 0,789 90-95 1.4 1600 25 0.1-0.2
40
2.42 0.002 1.21 1600 4 46 X lo6
1.5 6 1.77 60-70 1.4 300
20-25 0.15 13.6 1.6 0,002 0.8 180
7
1350 X lo6
of the mother liquid (1.5 to 2?& CHICHO) is somewhat higher than is possible with the higher temperature of the reactor in other processes. When the acetaldehyde content of the mother liquid is high, a large amount of resin formation would be expected a t the higher operating temperatures. This has not been observed in the present case, because of the relatively low temperature a t which the absorber operates. This is the highest temperature in this system. The loss of acetylene and the nuisance of separation and removal of by-products are minimized, owing to this low operating temperature. The hydration reaction of acetylene has some analogous reactions, such as those giving crotonaldehyde, acetic acid, and aldol condensation. These side reactions are highest when the reaction temperature is high. But experience shows that if the reaction temperature is kept below 60 O to 70 O F., these reactions are not important. In the Chisso process, where the purity of acetylene is kept over 99%, the formation of acetic acid can be kept under O.5y0. Crotonaldehyde formation and aldol condensation are functions of temperature and acetaldehyde concentration. Under these low reaction temperatures, crotonaldehyde formation is kept under 1%; and other aldol condensation is practically not existent. No established data have been reported on catalyst life. Through industrial experience and experiments, it has been found that the life of catalyst is shortened by elevating the reaction temperature; and the rate has some relation to the value of k,.
Excess Acetylene and Acetylene losses The German process evaporates acetaldehyde from the reactor with a stream of excess acetylene, utilizing the heat of the reaction. The reaction heat developed in the mother liquid is dependent on the reaction velocity, and thus in turn upon the ratio of total acetylene fed to that converted under the operating conditions. The presence of excess acetylene adds contact area for the reaction and increases the partial pressure of acetylene in the reactor. Thus, the temperature of the mother liquid depends upon the balance of the reaction heat available (which increases with higher reaction velocity a t higher temperatures) and the latent heat utilized in the evaporation of the acetaldehyde (which depends on the amount of excess acetylene sweeping through). This temperature may be independently increased by adding steam to the reactor in order to keep the reaction balanced by the evaporation of the acetaldehyde therefrom. VOL. 48, NO. 8
AUGUST 1956
1 26 1
Table 111.
Data of Design and Operation of Lorge Plant Using Chisso Process 1.8 5
R.p.m. Suction pms, mm. Delivery press, m . % g metem/hr. Suction volume, a. Com anents of mother liquid HSO4, % HgO, / 00cc ’ Total Absorbing temperature and p m e Evaporating temperature in vacuum atill, C. Pressure of vacuum still, mm. Hg Vapor at outlet of vacuum still, acetaldehyde, wt. % Temperature of vapor at suction of com 0 c. ~ressurcat suction of compmsor, mm. Vapor at outlet ofpartial condensing tower, acetaldehyde, wt. % Delivery pressure of turhocomprmor, mm. Hg Temperature at delivery of turbocompmor (controlled), 0 c. Condensing temperature at top of final rectifying column, C. Acetylene(99% (consumption 15’C., 1 atm.), (figun c o n w e d in 00% purity), eu. m. Actual power consumption (turbocompressor), hp. Actual power consumption (acetylene blower, drculation pump, etc.), hp. R& eration power for ”oling pxduct acetaldeh de to C. and maintaining at that temperature, l p . Acetaldehyde production, metric tons/hour Purity of acetaldehyde p x d u e d , wt. yo Power consumption per metric ton of acetaldehyde produced, without cooling of acetaldehyde, kw.br./ton Total power consumption per metric ton of acetaldchyde pmduced, with fooling of aectaldehyde, kw.. hr./ton Material m u m tion p a metric ton of acetaldehyde A- lene (at P s o c., 1 atm., 100 %), eu. meters H&a, kg. Mer-, kg. Steam consumption. None is used in rectification but a small amount may he used in regeneration o ‘ mother liquid. This quantity has not been meas wed direct1 ,hut is assumed to be about 200 kg. per ton ofacnddehyde.
i%,k
1
8’
Although this use of a large excess of acetylene is a good method for removing the acetaldehyde pmduced, the necessary subsequent processing requires a complex seties of operations for separating the mixed vapors of acetylene, water, and acetaldehyde into p u n products. The first step is condensing the evaporated mixed vapor for acetylene separation, but a small quantity of acetaldehyde escapes unless it is scrubbed with water. This water scrubbing introdurn a weak aqueous solution of acetaldehyde and dissolved acetylene, which has to be recycledafter separation and purification. This adds to the complicated separation and rectiiication equipment required to obtain acetaldehyde, and to the purification eqriipment required for recycling acetylene. I While no exact or complete material balance for the German process has been published, a simple material consumption has been indicated (S),without ddinite data as to acetylene consumption. It may be presumed, how-
1262
350 7000 200 1900 7000 15-25 0.14.15 2-4 66-73’ C. Ibov 64-68 230 About 70 About 35 205
mm. n g
About 86 1500-1900
About 90
densing tower between the vacuum still and the turbocompressor, and improving the design and materials of construction of the turbocompreasor, an almost indefinite life of the turbocompressor was secured. Table 111 gives data on design and operation of the large plant. Table 111 shows that the Chisso procegs has ’an acetylene a c i e n c y of slightly over 96.5%. Of the 3.5% loss of acetylem, a major amount is known to occur at one point; and this is now being corrected so that the efficiency of the new unit will be 98%, or higher, utilization of acetylene. A new turbohlower has been installed, which has given a lower power cost and other advantages. The essential details of the Chisno mcess are covered by granted and pending patents.
43
Nomenclature
720 280
C’
60 85 1.27-1.3 99.5
About 195 About 245
ever, that the process would have a larger loss of acetylene and acetaldehyde than in the fewer units and simpler processing of the Chiaso process as described above.
= gas concentration in liquid con-
tacting gas phase, cc.C&/cc. liquid dL = diffusivity of gas into liquid, sq. cm. per minute d = thickness of diffusion film,cm. K =DJd k. = reaction velocity constant, 100 cc. per gram pa minute = contact area (diffusional a m ) between gas and liquid, sq. cm. b‘, = volume of liquid in reactor, c c
dv
’
-=
rate of acetylene removal from system, cc. per minute
Acknowkdgment Thanks are due to Shin Nippon Chisso K.K., Ltd., for permission to publish these results. Acknowledgment is also due to the engineers for the research, the construction, and the operation of the plant at the Minamata factory of Shin Nippon Chisso for their cooperation in obtaining the design and operating data reported, and to Ronald C. Kowalski for his help with the manuscript.
Operating Dato of Chisso Process In the first plant utilizing the Chisso process, there was no fractional condensation tower between the vacuum still and the turbocompressor. It was for this reaction tower that the above calculations for absorption were made. The vacuum compressor was a multistage, stainless sreel turbocompressor of eight stages, each provided with injection water for cooling. The suction pressure was from 100 to 230 mm. of mercury and the pressure ratio was between 7.6 and 13. The compressor was rotated at 10,000r.p.m. by a 350-hp. motor. I n one test of 1 month’s duration, the plant showed an acetylene efficiency of over 96%. Later mercury vapor coming from the absorber was found to damage the turbocompressor. By inserting the fractional partial con-
INDUIRIAL AND ENMNEERINO CHEMISTRY
Literature Cited (1) Frieman, R. H., Kennedy, E. R., Lucas, H. J., J . Am. Chm. Soc. 59,
722 (1937). (2) Hatta, S., J. C h a . Soc. Japan 35, 35 (1932). (3) Kirk, R. E.,Othmer, D. F., “Encydopedia of Chemical Technology,” vol. I, Interacimce, New York, 1948. (4) Othmer,D. F., Luley, A,, IND.,ENO. CHEH.38,408 (1946). (5) Othmer, D. F.,Thakar, M., Did., 45, 589 (1953). (6) Shcrwood, Peter, P8trolem R t j m 34, No. 3, 201 (1955). (7) Ueno, S., Orido, Y., 3. Tokyo Ind. Lab. 36, No. 4 (1941). (8) “Ullmann’s Enzyklopedie der Tech\
nischen Cbemie,” Wilhelm Famt, ed., 3 Auf., 3 Bd., p. 2, Urban and Sehwartzmhcrg, Munich and Berlin, 1953.
RECENED for review November 4, 1955 ACCBPTBDMay 7,1956
