I N D U S T R I A L A N D ENGINEERING CHEAVISTRY
July, 1926
sible to prepare a standard solution by weighing out the exact amount of salt. A solution of about 0.2 N is desirable. This solution is prepared by weighing out about 16 grams of reasonably dry ammonium acetate, dissolving in absolute alcohol, and making up to 1 liter by adding the necessary amount of absolute alcohol. The solution is then standardized by titrating against pure CaO. The latter should be prepared by calcining pure calcite in a platinum crucible at 900" to 1000" C., the heating to be continued until constant weight is obtained. One-tenth gram of the freshly prepared CaO is placed in a flask with 25 cc. of alcohol, 5 cc. of glycerol, and 8 to 10 drops of phenolphthalein. The mixture is heated to boiling and titrated while hot with the ammonium acetate. If the CaO forms lumps on wetting, it may require reheating and titrating several times before all the lime enters into the reaction. The strength of the solution is then calculated in terms of grams CaO per cubic centimeter.
743
The titration of free lime in cement is carried out as follows: One gram of freshly ground cement is weighed out, placed in a flask with 25 to 30 cc. of absolute alcohol, 5 to 6 cc. of glycerol, and 8 to 10 drops of indicator. The mixture is heated to boiling, and titrated while hot with the standard ammonium acetate solution. The operations of boiling and titrating are repeated until the pink color does not reappear on boiling for several minutes. If only a small amount of free CaO is present in the cement, the pink color may not appear until after several minutes boiling, but if no color appears in 10 minutes the test may be considered negative. The total time required for the completion of a test may vary from a few minutes to an hour or more, depending on the amount of free lime present, the fineness of grinding, and the amount of glass in the cement. In every case the boiling should be continued until such time that the pink color does not reappear for several minutes after the final addition of ammonium acetate.
Cresylic Acid from Petroleum Distillates' By L. J. Catlin STANDARD
O n Co.
(KANSAS), NEODESHA,
T
HE presence of cresols and phenol in cracked distillates has been demonstrated by Brooks and Parker.2 This paper presents data obtained from samples produced in a continuous treating plant handling cracked distillates, where a wash of caustic soda was used as the first stage of the treating process. The oil was precipitated from the caustic by neutralization with hydrogen sulfide from still gases. It was found necessary to carry this reaction considerably beyond the neutral point to a condition where the alkali tested about 60 per cent NaHS and 40 per cent NaaS in order to get a ready separation of the oil from the solution. Even a t this point the residue liquor contained considerable quantities of oily products, which separated a t a high concentration of the alkali in the process of recovering the sodium sulfide. A distillation was made of the oil precipitated from the caustic solution using 500 cc. in an Engler flask. Between the temperatures 195" and 227' C., 10 per cent fractions were separated for further examination. All these fractions reacted positively to tests for cresylic acid as outlined by Allen.8 The fractions between 195' and 205' C. and between 205" and 210" C. had a specific gravity of 0.9951 and 1.0052 (l5'/15" C.) respectively, thus showing the absence of ortho-, meta-, and para-cresols. Further data on this distillation are shown in Table I. Table I (Specific gravity of sample, 1.058) Temperature Sp. gr. of O c. Per cent off 10 per cent fraction 101 10 water) 195 15 {water and oil)
205 210 212 219 226 227 232
25 35 45 55 65 75 82
0.9951 1.0052
Average (195' to 227' C.)
1.0134
1.0262 1.0270
Another distillation was made and the composite sample from 195" to 227" C. was redistilled in a 100-cc. Engler 1 3 J
Received March 16, 1926. 16, 587 (1924). Allen's Commercial Organic Analysis, 4th ed., Vol. 111. p. 316.
THISJOURNAL,
KANS.
flask in comparison with commercial samples as shown in Table 11. Table I1 -Cresylic Cresol
U.S.P. Sp. gr. (15'/15O C.) 1.033 Sulfur, per cent 0 .O Water, per cent 0.5 Per cent off
5 10 20 30 40 50 60 70 80 85 90 95
c.
97 per cent
1.032 0.098 2.0 Distillation 0
C.
Acid-
95 per cent
1.030 0.033 2.0
c.
194.5 194.7 195 195.5 196 196 196 196.2 196.7
196.7 197.2 198.3 199 199.5 200 201 202 204.4
196 197.3 200 201 202 205 207.2 211 217.2
l9+:2 197.7
208:3 214.7
231 246
...
Petroleum acid 1 ,0057
0.47 1.0
c. 205 205.5 206.7 208.9 210 211 212.8 215.6 218.3 221
... ...
The relation of specific gravity to boiling point on the petroleum acid suggests methylphenyl carbinol, (K) CH3(CBH~CHOH,specific gravity 1.003 (25O/25" C.), boiling point 218 to 220.4 Samples similar to the one reported in Table I1 were sent to various companies dealing in coal-tar products, one of which reported it as containing "87 per cent of tar acids of rather high boiling character." The oil has a very strong odor suggestive of mercaptan products, which is further indicated by its high sulfur content. In the process of recovering sodium sulfide from the spent alkali it was first necessary to add sufficient caustic to bring the KaHS up to T\'asS. When this was concentrated to a point indicative of 62 per cent NazS to suit commercial requirements for fused sodium sulfide, it was found that the residue of oily products was thoroughly mixed with and inseparable from the sodium sulfide. It was found, however, that if the concentration was stopped a t a boiling point of 143" C., and the mix allowed to cool, there was a very sharp separation, with the oily products collected at the surface and sodium sulfide of commercial purity solidified below. At a temperature as much as 10" C. below or above this 4
Olsen, Van Nostrand's Chemical Annual, 1918.
744
INDUSTRIAL A N D ENGINEERING CHEMISTRY
point, the separation was incomplete and the sulfide contaniinated. After removing the impurities it was necessary to resume the concentration of the sodium sulfide, carrying the temperature to about 222’ C. to produce the 62 per cent fused sodium sulfide of commerce. The economy of the practices here described in refinery operation is dependent upon a great many factors, not the
Vol. 18, No. 7
least of which is freight charges to possible consumers of the products; but a point not to be overlooked is the reduction in sewage pollution of small streams or larger bodies of water near city water supplies. The amount of cresylic acid of the grade described in Table 11, which may be recovered by the methods here outlined, is in the neighborhood of 0.00678 per cent by volume of the pressure-still distillate treated.
Absorption and Desorption of Ammonia in a CokePacked Column’ By T. K . SherwoodZand A. J. Kilgore MASSACHUSETTS INSTITUTE
OB
TECHNOLOGY, CAMBRIDGE, MASS.
HE important diffusion Wide possibilities are apData are presented on the absorption and desorption processes, in which a parent in the development of of ammonia gas in a column packed with 9 to 16 mm. the relationships between the gas or volatile material coke. The capacity coefficient of the column increased mechanisms and rates of abdiffuses to or from a liquid, from 1.45 to 4.39 grams ammonia diffusing per hour sorption and rectification, for are absorption, desorption, per cubic centimeter per atmosphere partial pressure d i f f e r e n t liquid-vapor sysr e c t i f i c a t i o n , and steam difference, while the gas velocity increased from 12.1 to tems, under various condi‘(stripping.” Absorption in41.3 kg. per minute per square meter of total cross secvolves the diffusion of the gas tions. The development of tion of the column. The liquor velocity was maintained s u c h r e l a t i o n s h i p s would or volatile material from the constant a t 26.3 kg. per minute per square meter of make available large amounts gaseous to the liquid phase, total column section. The average gas temperature of data on the performance of and may be accompanied by was approximately 32’ C., and the liquor temperature absorption apparatus for use t h e d i f f u s i o n of a small averages 21 to 25 a C. in the design of rectifying amount of vapor of the solA t the same gas and liquor velocities, the capacity columns, and vice versa. vent, either from gas to liquid coefficient of the column for absorption was found to be As a first step towards the or from liquid to gas. Dethe same as for desorption, within experimental error. establishment of these relasorption is the name given tionships under special conto the reverse process, the evolution of a gas or volatile material from a solution, which ditions, the experiments described belbw have been carried may also be accompanied by the diffusion of a small amount out, to determine the relation between the rates of diffusion of vapor of the solvent, to or from the liquid. Rectification of ammonia gas to and from a dilute aqueous ammonia soluinvolves the diffusion of both volatile material and vapor of tion in a coke-packed column. the solvent to and from the solution. More of the less Experimental volatile material diffuses from the gas to the liquid than from liquid to gas, and a greater amount of the more volatile maThe apparatus (Figure 1) consisted of an iron pipe, inside terial diffuses from liquid to gas than the reverse, so the net diameter packed for 107 of its length with 9effect is the diffusion of relatively large amounts of less vola- to 16-mm. household coke. The liquor feed, which was tile from the gas to liquid, and the evolution from the liquid Tvater in the absorption runs and dilute ammonia solution in of the heat equivalent of the more volatile. Stripping with the desorption runs, was fed at a rate to the top steam is a special case of rectification, in which the original of the columnand was distributed Over the packing by means gas contains none of the volatile material to be removed from of a tin cup, The rate of feed was maintained the liquid. constant in all runs a t 216 grams per minute, corresponding The similarity of the processes of absorption and to 26.3 kg. per minute per square meter of total cross-sectional tion has been pointed out before, but little attention has been of the column (5.39 lbs. per minute per square foot). given the possibility of using data on absorption and ret- The solution leaving the column was collected in one of two tification interchangeably in the design of absorption and ret- 5-gallon bottles, the gas space of each bottle being connected tifying columns. to the column by tubing in order to equalize the pressures in Received March 2, 1926. the bottles and column. Research Associate, Department of Chemical Engineering, MassaAir was supplied by a positive pressure blower, and measchusetts Institute of Technology, Cambridge. Mass.
T
O
1
Table I-Absorption PARTIAL PRESSURE Temp. of NHJ PRESSURE IN TOWERliquid Total NHs NHs Input Ingas Ingas AtbotAt atbottom difin gas output NHs NHa leaving entering tom top of tower leaving “a, G./1-in. fusing C. Run bottoms G./min. G./min. G./min. G./min. Mm. Hg Mm. Hg Mm. Hg Mm. Hg 7.78 26.4 799.2 790.4 25.5 6.65 22.35 4.82 1.9s 6.80 1 7 8 5 . 1 2 6 .7 8.32 29.0 794,O 6.75 22.76 4.90 1.92 6.82 2 8.32 31.25 788,O 783.0 28.0 6.65 1.60 6.50 22.72 4.90 3 7 8 2 . 1 2 8 .8 9 . 3 9 3 7 . 9 7 7 8 . 2 6 . 5 5 5.12 1.62 6.74 23.70 4 27.4 8.78 42,35 785.0 781.0 6.55 5.44 1.35 6.79 25.20 5 36.2 772.0 769.0 27.7 5.08 4.74 4.76 18.80 4.10 0.66 6 2.57 57.0 768,O 768.0 28.6 4.85 4.54 0.21 4,75 21.25 7 5.08 40.9 771.0 769.0 4.74 28.0 4.30 0.62 4.92 19.75 8 25.16 787.0 781.0 25.5 6.45 6.54 1.41 5.93 21.20 4.52 9 6.45 32.8 779.0 775.0 26.6 6.22 22.90 5.00 1.14 6.14 10 6.54 24.7 790.0 780.0 26.8 6.72 1.62 6.21 21.05 4.59 11
Air velocity Gas velocity Partial Lbs./rnin./ pressure K /min. over Ka fiq.rn. Ka sq. f t . Lbs./hr./ total bottoms G./hr./ total area Mm. Hg cc./atmos. area cu.ft./atmos. 201 8.45 18.6 3.22 41.2 182 7.64 19.8 2.92 37.3 32.6 161 6.68 19.7 2.58 137 5.63 22.6 2.20 27.5 132 5.05 23.1 2.12 24.6 125 4.11 2.00 20.1 17.0 102 2.47 1.64 12.1 20.1 18.2 1.89 17.9 118 3.66 7.65 37.4 215 17.9 3.45 185 5.80 20.1 2.97 28.4 229 8.19 3.68 40.0 18.2
