330
INDUSTRIAL A N D E N G I N E E R l N G CHEMISTRY
Frey, F. E., and Smith, D. F., Ibid., 20, 948 (1928). Groll, H. P. A,, Ibid., 26, 698 (1934). Hague, E. N . , and Wheeler, R. V., Ibid., 26, 697 (1934). Hague, E. N., and Wheeler, R. V., J . Chem. SOC., 1929, 378. Hurd, C. D., IND.ENQ.CHEM.,26, 50 (1934). Hurd, C. D . , and Goldsby, A. R., J . Am. Chem. sot., 56, 1812 (1934). Ipatiew, W., Ber., 44, 2978 (1912). Kassel, L. S., J. Am. Chem. Soc., 54,3949 (1932). Krause. M. V.. Nemtzov. M. 5..and Soskina. E. A,. ComDt. rend..acad. sck. U.S. S.k., 2,305 (1934) ; J . den. Chem. U.*S. S. R., 5, 343 (1935). Lenher, S., J. Am. Chem. SOC.,53, 3737 (1931). Lewes, V. B., PTOC.Row SOC.(London), 55.90 (1894). Ibid., 57, 394 (1895). Magnus, G., P o g g . Ann., 90, 1 (1853). Marchand, R. F., J . prakt. Chem., 26,478 (1842). Melville, H . W., Trans. Faraday Soc., 32, 258 (1936). Mignonac, G., and Saint-Aunay, R . V. de, Compt. rend, 189, 106 (1929). Norton. L. M.. and Noves. A. A.. Am. Chem. J.., 8.362 (1886). , . . Pease, R. N . , j . Am. CheA. S O C . , ’1158 ~ ~ , (1930).
to any great extent, why should both propylene and methane be low in the nitrogen dilution experiments? The formation of -CHz-CHzradicals, suggested by Hurd (I@, were not observed by Rice (33) when he passed freshly decomposed ethylene over metallic mirrors, the method commonly relied upon for showing the presence of free radicals. The formation of the CHz -CHand -CH=CHradicals of Berl and Forst would involve extremely high energies of activation and they are quite improbable. The authors do not wish to deny, however, that free radicals may play a part in the polymerization of ethylene in the presence of decomposing metal alkyls, etc.
Acknowledgment Acknowledgment is gratefully made to E. I. du Pont de Nemours & Company, Inc., for financial assistance extended to C. H. Whitacre for the prosecution of a portion of this work.
Literature Cited Berl, E., and Forst, W., 2.angew. Chem., 44, 193 (1931). Berthelot, M., Bull. SOC. chim., [2] 6, 280 (1866). Bone, W. A., and Coward, H. F., J . Chem. SOC.,93, 1216 (1908). Buff, H., and Hofman, A. W., Ann., 113, 143 (1860). Cramer, P. L., J . Am. Chem. SOC.,56, 1234 (1934). Damon, G. H., IND.ENQ.CHEM.,Anal. Ed., 7, 133 (1935). Davidson, J. G., J. IND.EXQ.CHEM.,10, 901 (1918). Day. D . T., Am. Chem. J.. 8. 153 (1886). Dunstan, A.E., Hague, E. ‘N.,and Wheeler, R . V., IND.ENQ. CHEM.,26, 307 (1934). Dunstan, A. E., Hague, E. N . , and Wheeler, R. V., J. SOC. Chem. Ind., 51, 131-3T (1932). Dunstan. A. E., Hatrue. E. N . , and Wheeler, R. V., World Petroleum Congress, London, 1933, 2, 77. Fischer, F., and Pichler, H., Brennstgf-Chem., 13, 381 (1932). Frey, F. E., and Hepp, H. J., IND.ENQ.CHEM.,25, 441 (1933).
VOL. 29, NO. 3
\--I
-Thdd.. --~
53. - - , 613 _ - _(19.11). \ - - - - I -
(33) Rice, F. O . , and Rice, 0. K., “Aliphatic Free Radicals,” p. 43, Baltimore, Johns Hopkins Press, 1935. (34) Rice, 0. K., and Siokman, D. V., J. Am. Chem. SOC.,57, 1384 (1935). (35) Schneider, V., and Frolich, P. K., IND. ENG. CHEM.,23, 1405 (1931). (36) Storch, H. H., J.Am. Chem. SOC.,56, 374 (1934). (37) Ibid., 57, 2598 (1935). (38) Taylor, H. S., and Jones, W. H., Ibid., 52, 1111 (1930). (39) Tropsch, H., Parrish, C. I., and Egloff, G., IND.ENQ. CHEM., 28, 581 (1936). (40) Walker, H. W., J.Phys. Chem., 31, 961 (1927). (41) Wheeler, R. V., and Wood, W. L., J. Chem. SOC.,1930, 1819. (42) Wilde, M. P. de, Bull. soc. chim., [21 6 , 267 (1866). (43) Zanetti, J. E., Suydam, J. R . , and Offner, M . , J. Am. Chcm. SOC.,44, 2036 (1922). RECEIVED September 26, 1936. Presented before the Division of Petroleum Chemistry at the 92nd Meeting of the Amerioan Chemical Society, Pittiburgh, Pa., September 7 t o 11, 1936.
Anomalous Behavior of
Mortar Coats E. ABEL AND F. HALLA I n s t i t u t fur physikalische C h e m i e a n der T e c h n i s c h e n H o c h s c h u l e , V i e n n a , Austria
T
HIS paper deals with the anomalous behavior of mortar which the authors have occasionally been called upon to investigate. This phenomenon will not be met often, but the method of investigation is of general interest and may be useful in solving similar problems. I n certain houses built and finished a t the same time, the following defect was found in the plaster of various rooms: Flat circular pieces of mortar about 8 inches in diameter peeled and fell off. I n its latent state this defect was indicated by cracks nearly circular in shape. Upon removing one of these defective patches with a knife or scoop, without exception a core, either lighter or darker than but always different in color from its surroundings, was found a t the bottom of the hole. The core was powdery and crumbled a t touch. Some of the cores showed a distinct hull, easily discernible from the middle part by its deeper hue. Sometimes the core could be extracted partially or wholly with the rest of the
Physico=Chemical Explanation faulty material, and it was obvious that the core was a foreign substance in an otherwise homogeneous material. Wherever there was a defective part, there was also a core. This fact reduced the question of the cause of this defect to the investigation of the nature, effect, and origin of the core.
Nature of the Core The cores were situated underneath the surface of the plaster a t different depths; the greater the depth as a rule, the greater the deteriorating effect of the core. If the core happened to be covered by a rather large stone in the mortar, the stone acted somewhat as a shield, so that the deteriorating effect covered a greater area and was therefore specially obvious. The color of the core varied between yellow and nearly black; the lighter cores were the most frequent. By removing the core with a small sharp-edged knife, no other material was included. Under the microscope the light cores appeared to be a conglomerate of transparent, shining particles without crystal structure, but in polarized light they were found to consist chiefly of calcite (CaC03).
, ,/’
,/’” 331
INDUSTRIAL A N D ENGINEERING CHEMISTRY
MARCH, 1937
Thus the raw material was the same marly limestone for the unaffected as well as affected material. The degree of Gray Black Light carbonization, however-that is, the degree of hardening of Core Core Core the cores-was essentially less than that of their unaffected Heat loss (COP + a little moisture) 26.72 20.12 17.14 surroundings, in agreement with the writers’ theory. This Si01 5.47 14.20 18.31 3.37 4.40 Fez08 1 09 result could be verified under the microscope after addition A1208 1.43 5.01 4.82 62.42 55.28 53.53 of phenolphthalein solution by the deeper red color of the CaO 7 18 2 OR 1 77 Ma0 parts carbonized to a lesser extent. Total But there are considerable differences in the degree of carbonization of the different kinds of cores, according to their OF (UNBURNED) LIMESTONE color (as shown by their marly contents in Tables I1 and 111). TABLE 11. PER CENTCOMPOSITION The higher the percentage of these marly substances, the Light Gray Black Core Core Core lower the relative carbon dioxide content: TABLE I . PERCENTCOMPOSITION OF THE CORE
90.0
78.5
Light Core 2.32 1.22 52.3
Alkaline equivalents, % COz equivalents % Degree of oarbohiation, ’%
TABLE 111. PERCENTCOMPOSITION OF BURNED SUBSTANCE CaO MgO Fez03 Si01 AlnOa Total
Light Core 86.0 3.0 ::!]14.l 2.0 100.1
-
Gray Core 69.2 2.5) ‘!):j30.7
99.9
Black Core 64.5 2.2 2g:i/35.4 5.8 99.9
The analysis of the cores (always average samples of several cores of similar color) given in Table I shows which component of the raw material (of the unburned limestone) produced the cores. By calculating the carbonates, based upon the alkaline earth oxide content of the cores (after subtracting the heat loss), the original weight of the limestone and its composition are found (Table 11). Therefore the core always originates from a marly, clay limestone. If the composition given in Table I is calculated for the burned lime, free of carbon dioxide (and moisture), the figures in Table I11 result. This composition demonstrates that the burned lime did not correspond to the Austrian standard, according to which white lime should not contain more than 10 per cent magnesia and silicate components (“silicate formers”-silica, alumina, ferric oxide) together. According to Table I11 this content is three to four times greater than the standard. On the other hand, these results do not mean that the average composition of the lime was not the normal one. Of course the usual causes of defects in lime mortar had to be considered-sulfur content and the presence of fungoid vegetation-but no trace of them was found even by the most sensitive means.
Behavior of the Core Careful consideration of the deteriorating effect of these cores made it certain that the core was the cause of the defect in the plaster. This effect can be due only to the absorption of carbon dioxide by the core mass which is accompanied by a relatively large increase in the core volume. Therefore, the carbonization of the cores should be essentially less than the carbonization of the surrounding material. Of course the degree of carbonization must not be calculated on the basis of the actual carbon dioxide content (Tables I V and V), because the materials in the core capable of combining with carbon dioxide are different from those in the surrounding material. Therefore only the relative contents of carbon dioxide must be taken into account, as shown in Table VI. The prerequisite of equal age of all parts was fulfilled in this caBe.
Black Core 1.98 0 50 25.2
Gray Core 2.08 0.92 44.2
The immediate cause of these effects is clear-a different degree of carbonization in different parts of the plaster and less carbonization in the cores. This behavior involves a retardation in the hardening process of the cores and there. fore occurrence of local tensions. Causes of Anomalous Behavior
Since the cores and the surrounding plaster came from the same raw material, the differences in the carbonization can be due only to differences in the capability to absorb carbon dioxide-that is, differences in the lime with regard to the rate of Carbonization. I n the present case these differences could have originated from chemical peculiarities as well as from mechanical ones. CHEMICAL PECULIARITIES. It is well known that the absorption of carbon dioxide, which causes hardening, is chiefly a carbonization of calcium hydroxide. Dry lime (CaO, the burned limestone) absorbs carbon dioxide only a t a very slow rate; besides, the incrustation by the resulting CaCOa prevents the further progress of the carbonization. ComPERCENTCOMPOSITION OF Two LIGHT CORESAND OF THE SURROUNDING PLASTER
TABLEIV.
--
Core 27.8 10.36 2.63 2.71 55.06
coz
Si02 Fez08 AlzOa CaO MgO Total
... -
98.56
--
A-Surrounding plaster 36.14 9.40 1.97 1.88 45.24 3 .96 __ 9 8 . 59
Core 29.61 7.53 1.62 3.10 54.84 1.68
m
B-----. Surrounding plaster 36.78 7.16 1.41 1.56 46.82 3.01 @6y7z
TABLE V. PERCENTCOMPOSITION OF (UNBURNED) LIMESTONJJ FROM
WHICHTHE MATERIALS OF TABLEIV ORIQINATED A
CaCOs MKCOS Si02 Fen08 AlzOa Total
Core 86.6 86,
...
1
9.1 2.3 2.4
100.3
Unaffected surrounding plaster 79.0 8 . 3 ) 87‘3 9.2
1.9 1.9 100.3
.--
Core 86 0 3 : l j 89‘1 6.6 1.4 2.7 99.8
B Unaffected surrounding plaster 83.6 6 . 3 1 89.9 7.2 1.4 1.6 1307
TABLE VI. DEGREEOF CARBONIZATION 7 -
Alkaline equivalent, Yo COz equivalent, Yo , Degree of carbonization, % ’
Core 1.97 1.26 64.3
8----. Unaffected surrounding plaster 1.82 1.64 90.0
7 -
Core 1.98 1.36 68.7
B.Una%e&+ surrounding plaster 1.82 1.68 92.5
INDUSTRWL AND ENGINEERING CHEMISTRY
332
plete hydration of the original CaO to Ca(OH), is tlierefore the condition for proper binding. As the process of slaking does not fulfill this condition completely, the moistened lime must have time to terminate the hydrating process (soaking). The slower the slaking, the longer is the time necessary for soaking the lime in the slaked state. If there are still unslaked lime particles in t h e mortar, even after previous slaking and soaking, the rate of hardening of these particles is obviously that of their carboniz a t i o n . But since this is, in effect, dependent on the presence of calcium hyd r o x i d e , carbonization cannot take place quicker than hydration; where u n h y drated CaO e x i s t s , the rate of carbonizaFIouRE 1. hCRWSTEU PARTIDI& tion ( h a r d e n i n g ) is GX~OCSD d e t e r m i n e d by the Dotted h e r *e srate inoruatstion from rate of the reaction: dead-bamed &O i n middle portion. CaO
+ ILO --+
Ca(OH)*
This rate most be very slow for, in tho advanced state of the hardening process, unhydrated lime particles can be present only if particles are present whicli during slaking and soaking did not absorb water. Obviously the presence of unchanged unhydrated CaO cannot be proved by chemical methods, since the separation of hygroscopic (free) and chemically (stoichiometrically) absorbed water is practically impossible. This difficulty is overcome by x-ray analysis, owing to the difference in the lines originating from the CaO molecule and those from Cn(OII),; this difference enables distinction between those compomiils. Under tlie conditions given in Table VI1 s-rny pou;der diagrams were made from light e w e s and were compared with the diagrams of CaO ( I ) , Cn(O€S),, and CaCOs (2). The result showed that unhydrated CaO was present in tlie core, since some of the lines are those of CaO. Tiierefore, the unhydrated h e particles were the primary cause of the delects in the plaster, a result which could be shown only by x-ray analysis. As to the origin of these lime particles in the light cores, no process can be held responsible other than ttie burning of the lime which, when not properly conducted, obviously caused the material to be partly deail-burned. MECHANICAL PECULIARITIES. A dark xrray covered core from the surrounding substance was separated from the
VOI.. 29, NO. 3
plaster in such a way that. the structure remained unchanged and could be examined microscopically. On tlie periphery (of the core) was a dark incrustation (Figure 1) which came from the conversion of the limestone in an enamel- or clinker-like material, obviously formed during burning. Thus an incrustation was formed which, acting as a protective covering, delayed the hydration of the enclosed lime particles and also the carbonization; thus the hardening process was retarded considerably. As the result of this investigation, we can say that the defects in question were caused by the use of a mortar containing particles of lime which escaped hydration during slaking and soaking, effected by the burning process.
m e e t of Intermediate Processes Although there is no doubt that the raw material and burning are responsible for the defects in the mortar, the question arises as to whether the intermediate processes of slaking, soaking, and sieving could not have counteracted the detrimental effects of burning. This question should probably be answered in the affirmative because of the following results of sieving: Ordinary commercial white limewas well slaked in the usual way, soaked 3 days, and carefully sieved throng11 ‘/,-inch mesh; a considerable amount of lime remaincd on the sieve. The sieved lime was mixed with sand in the proportion I to 3 and the mortar thus obtained was put into small wooden frames. Sothing unusual occurred (upper part of Figure 2). But when asmall grain from therriortarrernaiiiingon tliesieve was inoculated into the otherwise iinaffected mortar, the latter soon behaved exxctly as the affected mortar described
17IOUHE
2.
S.\Mi’LE
or: M
:)IrrAB 1.LVE
,‘no\,
m-~;r.,.-sL,tiE,,
The lower part _a6 iiioculkted a described.
TABI.E VII.
X-RAYPOWDEB DIAGRAM (DEBYE-SCHERRER) OF I ~ I I CORES T
Film 2da 0 Fouirdh 0 Cs1od.G Index Cu-K Radiation (Ag”iied tension, 40 kv. effective: load, 16 ma.: time of mP08“‘e. 5 IIUUTJ! 1). s. 90 39.4 18-36, 18%1’ 200 D. s. 20 64.4 27-6’ 2708’ 220 Fe-ti llndintion Ileenlcd. to Cu-K Redi&ion
Distance of corresponding lines on the film: 1 m m . = 2’. B ia the angle of refleation. Caloulated from the lattice ennirtnnt of CsO(a = 4.77 A,! for thecrystallographic pllane (hkl) 88 indicated in the isat oolumn. a
b
in ttie foregoing paragraphs. Starting from this inoculated gray particle, cracking took place which caused peeling after 24 hours. This effectis shown in the lower part of Figure 2. The fact that cracking here leads tospiittingratlier than to circular peeling (as observed on the plastered walls) may be ascribed to the fact that with this cxperimerit tliree grains mere inoculated so close together that they disturbed one another. Finally the mortar remaining on the sieve was osed to prepare mortar in the same way. Peeling took place again, but it was less intensi7.e than in ttie previous case, because the concentration of the inoculated particles was too great to
MARCH, 1937
IKDUSTRIAL AND E N G I N E E R l N G CHEMISTRY
333
produce the full defects. Obviously the relative difference in hardening between core and surrounding material is important; the insulated unhydrated lime particles, embedded in an unaffected material, are the special cause of the destruction. These experiments are described to show the effect of the intermediate processes between burning and preparing the mortar. More careful sieving could have prevented the defects, a t least in part, and no doubt better slaking and larger soaking could have had a similar effect.
3. X-ray analysis showed that the cores contained unhydrated lime (CaO) in spite of previous slaking and soaking. 4. A clinkered covering was formed during the burning process which delayed hydration. 5. The behavior mentioned in conclusion 2 is kinetically connected with that of 3 and 4. 6. The deteriorating effect of unhydrated particles of lime embedded in an unaffected mortar was demonstrated experimentally.
Conclusions
Literature Cited
1. Certain mortar defects are explained by the presence of insulated cores embedded in the mortar. 2 . These defects were the result of the core material being carbonized less than the surrounding material.
(1) Gerlach, W., Z . Physik, 9, 188 (1922). (2) Olshausen, von, 2. Krist, 61, 490 (1925). RECEIVED August 10, 1936.
POTASSIUM NITRATE FROM POTASSIUM CHLORIDE AND NITROGEN PEROXIDE
DONALD L. REED AND K . G . CLARK B u r e a u of C h e m i s t r y a n d S o i l s , U. S. D e p a r t m e n t of Agriculture, W a s h i n g t o n , D . C.
P
RESENT-DAY chemical technology is making possible the synthesis of compounds formerly considered too costly for general fertilizer use. These possibilities and the trend toward the use of more concentrated fertilizers are arousing interest in new products as a source of valuable plant foods. Potassium nitrate contains nitrogen and potassium, two important plant food elements, and has physical and chemical properties that make its use in fertilizer mixtures advantageous. Whittaker and Lundstrom (18) pointed o u t that, although these properties of potassium nitrate have long been recognized, its cost of production has limited its use for fertilizer purposes. The advent of low-cost ammonia, resulting from the development of the synthetic process, has made possible the consideration of ammonia as a source of nitrogen for the production of potassium nitrate. Numerous articles and patents have recently appeared on such processes (1, 3,
I , 10, 11, 19).
As early as 1926 the Bureau of Soils considered the problem of potassium nitrate production from potassium chloride and nitric acid or oxides of nitrogen derived from ammonia oxidation. Mehring, Ross, and Merz (6) investigated the conditions suitable for the direct treatment of potassium chloride with nitric acid and obtained good yields of potassium nitrate; but they were unable to prevent loss of nitrogen, a portion of which was volatilized (as nitrosyl chloride and nitrogen oxides) with the hydrochloric acid resulting from the reaction. Whittaker, Lundstrom, and Mera ( I S ) considered the thermodynamics of the reaction: 2NOz(g.)
+ KCl(5.)
+ KNOa(s.)
+ NOCl(g.)
and found that it should proceed as indicated. Their experimental results showed that in the absence of moisture the reaction between pure nitrogen peroxide gas and solid potassium chloride ceased before appreciable quantities of potassium nitrate were produced. With 3 per cent of water present in the potassium chloride, however, good conversions were obtained.
A study has been made of the factors influencing the conversion of potassium chloride to potassium nitrate by the passage of nitrogen peroxide-air-nitrogen mixtures, derived from the oxidation of ammonia with air and ranging in cornposition from 5.2 to 1 1 .O per cent nitrogen dioxide by volume, through beds of moistened potassium chloride. Under comparable conditions of particle size, moisture content of the chloride, diameter and depth of the bed, and rate of flow of the nitrogen peroxide the more concentrated peroxide mixtures reacted more rapidly but less completely in a single pass than the less concentrated mixtures. Stepwise countercurrent nitration, with oxidation chambers between successive beds, indicated complete reaction of an 8 per cent peroxide mixture when half of the nitrogen oxides were converted to potassium nitrate and the other half to nitrosyl chloride. Mirkin ( 7 ) produced potassium nitrate from potassium chloride by passing concentrated mixtures of nitrogen peroxide (9 to 90 per cent by volume) and air through beds of potassium chloride crystals that contained various amounts of moisture. He met with only moderate success, and, partially because of limited facilities, his yields of potassium nitrate were low and recovery of nitrogen poor. He concluded that moisture was an important factor in the reactions, probably because it
