Apparatus and Methods for Precise Fractional-Distillation Analysis IV. Standardization of Low-Temperature Fractionation-Analysis Apparatus and Method Using Automatic Recording and Control WALTERJ. PODBIELNIAK, P. 0.Box 567, Tulsa, Okla. The operation of fhe Podbielniak apparatus sure readings, and turns out a complete printed for low-temperature fractional-distillation analysis fractionakdistillation curve, including a distillaof gases and volatile liquids has been standard- tion time rate curve. The robot is 80 to 90 per cent automatic, conized by the use of a n automatic recording and control mechanism, together with a further de- ducts distillations in less time, and is more development and standardization of the fractionat- pendable and accurate than the human operator. ing unit itself. After the sample is in the Through the use of this automatic recorder and column, the robot operator controls reflux cool- control, the complete standardization of the lowing, regulates distillation rate according to the temperature fractionation-analysis method resolves dijjculty of fractionation, summons the human ilself into the problem of deciding on sample sizes, operator with a buzzer and trouble light when- distilling tubes, and a f e w adjustments of the operatever necessary, takes all temperature and pres- ing mechanism.
T
proper specifications (3). The left-hand column is intended to be used for gas analysis, and is provided with a train of spiral caustic wash bottle and two dryin tubes, one usually filled with calcium chloride and the other witf either phosphorus pentoxide or dehydrite. This washing and dr ing arrangement is more efficient than that previously describe$ and is essential with automatic operation to prevent traces of carbon dioxide or water vapor in the gas samples freezing and obstructing the column. The provision of two columns on tap is convenient for alternate analysis of small gas samples and large gasoline or oil Samples, inasmuch as a 2.6-mm. inside diameter tube may preferably be used for the former together with a 5-cc. distilling bulb, while a 4.0-mm. inside diameter tube with a 1000-cc. distilling flask may be used for the latter. Furthermore, mounting the two columns compactly on the same side is necessary in order to keep distillate flow lines as short as possible from the automatic control mechanism to either column. The connections from the tom of the fractionating column distilling *tubes to the upper stopcock manifold have been made 1 mm. bore with no excess dead space to introduce lag in the distillate measurements and excessive hold-up (3'). For the same reason the glass tubing connections between stopcocks 5-2 and 8-3 have been made 2 mm. in bore, and the distillation pressure manometer tubing of a proximately 3-mm. bore. While not stown in the diagram, a special distillation pressure manometer with a nipple connection a t bottom and a mercury leveling bulb is provided for use with the micro 2.6- or 3-mm. distilling tubes, in order further to decrease dead space. To the left of stopcock 5-3, the requirement for maintaining the dead space at a minimum becomes much less stringent and the connections are therefore made of much larger bores (3 to 4 mm.) to facilitate evacuation and flow of vaporous d i s t i l l a t e . These apparent1 minor improvements are essential if the h l accuracy of the autom a t i c control mechanism and of the S t a n d a r d Precision columns is to be utilized. FIGURE1. STANDARD PRECISION APThe distillate-receiving manometer is of PARATUS FOR LOW-TEMPERATURE FRAC- the reevacuable type-that is, the vacuum TIONAL-DISTILLATION ANALYSIS end is sealed with a special mercury-seal
HE present article describes an automatic recording and control mechanism in conjunction with an improved and standardized low-temperature fractionaldistillation analysis apparatus, developed as the result of a comprehensive investigation (3) of all the fundamental variables or factors affecting the accuracy of the batch fractional-distillation method of analysis with the purpose of completing the development and standardizing the design of the apparatus and its parts, and adapting it to automatic operation, thus effecting substantial standardization of procedure. However, the automatic recording and control mechanism may be used with any low-temperature fractionating column designed for direct reflux cooling (No. 6, Figure 16, Nos. 8 and 9, Figure 17, Part 11). The fractionating unit shown in Figures 1 and 2 has been called the Standard Precision model because it has been designed specifically for highest practicable precision and standardization, w h e t h e r manually or automatically operated. Two Standard Precision low-temperature metal reflector-type lseparate vacuum jacket and distilling tube construction) f r a c t i o n a t i n g column assemblies are mounted on the right side of the apparatus in such a manner that either column may be used for analysis by simply turning stopcock 8-2 a n d interchanging thermocou le and heater wires. Both cof&nns are of the same general construction and may be ada ted for any kind of low-temperature ana&& by simply inserting distilling tubes and flasks of 1 Book rights reserved except by permission of author.
The apparatus described in this paper are covered by foreign patents and pending United States and foreign patent applications and are manufactured and distributed exclusively by the inventor.
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RH EO STAT
FIGURE2. DIAGRAM OF STA .NDARD PRECISION APPARATUS stopcock. Whenever the vacuum deteriorates sufficiently to affect the readings or when the mercury becomes dirty, it is a simple and convenient procedure t o remove mercury, clean manometer, pour in clean mercury, and reevacuate through the stopcock, using merely a suitable rotary oil pump such as the Cenco Hyvac. All this may be done without necessarily dismounting the manometer from the apparatus. It is not necessary to obtain a higher vacuum than about 0.01 mm. of mercury in the vacuum space. The long arm of the manometer is preferably calibrated and graduated by etching on the glass, to read directly in millimeters of mercury at 0' C. absolute pressure. For precise work correction should be made for effect of changing mercury level on vapor receiving system volume. This type of manometer is convenient and accurate for manual operation. For automatic operation, it serves only as a check on the special compensated manometer incorporated in the automatic mechanism (Figure 4). The fraction-collecting buret arrangement shown in Figure 2 is included in the Standard Precision model because of its convenience and accuracy in the analysis of highly complex samples by the procedure of breaking up the sample by fractional distillation into comparatively simple fractions containing very close-boiling components (or constant boiling point mixtures), and analyzing these fractions further by supplementary tests such as oxidation over copper oxide, absorption over reagents, etc. When the distillate is collected in these burets, the automatic apparatus applies only
to control of reflux cooling and distillation pressure and to indicating reflux temperature. The fractionating columns are of the Standard Precision metal reflector type (Figure 17, Part 11,S). Standard specifications have been recommended both for the vacuum jacket and for a range of distilling tubes, including complete data on liquid and vapor hold-ups, maximum distilling capacities, and fractionating characteristics. For any definite analytical requirements of accuracy and sample size it is possible to select a distilling tube of proper specifications. Automatic reflux cooling and control of distillation pressure positively require the use of the radiant dry packing type of cooling vessel and reflux chamber arrangement, shown in Figure 4, Part I (2), and further developed as described under Figure 17, Part I1 (S). Any type of gasoline or liquid reflux bath, such as used with the Regular, C. N. G. A., or spiral modifications (Figure 16, Part 11) is inherently unsuitable for automatic operation because of the large time lag between entrance of refrigerant to the cooling vessel and the consequent cooling of reflux vapor and drop in distillation pressure. This difficulty may be overcome only by complicated devices, and therefore no provision has been made in the automatic mechanism for operation of other than Standard Precision or Precision fractionating columns. The Standard Precision apparatus (Figures 1 and 2) is arranged for manual operation. To convert it to automatic
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ANALYTICAL EDITION
operation, it is only necessary to make certain connections as shown in Figure 4. For a complete description of the theory and details of manual operation of the distillation unit, the reader is referred to Part I (9). A fairly large human element necessarily enters into the operation. The effect of the human element on the analysis results may be minimized by standardizing as much as
FIGURE 3. AUTOMATIC RECORDER AND CONTROLFOR OPERATINQ LOW-TEMP E R A T U R E FRACTIONAL-DISTILLATION ANALYSISAPPARATUS possible on such details as sizes of samples to be taken, rates of distillation for various separations, exact method of changing distillation pressure, etc. ; by standardizing the apparatus itself by careful training of the operator; by frequent checking of the operator’s results against duplicates by same or other operator or against synthetic mixtures or against other methods of analysis. However, it will be obvious that the substantial elimination of the human element by the development and use of an automatic control and recorder is the logical solution to operational difficulties, either through direct use substantially to replace the human operator or through its tendency to lead to a better understanding of the principles of operation and to furnish an authoritative basis for comparison of fractionation unit modifications and adjustments and for standardization of manual operation. DESCRIPTION OF APPARATUB AND OPERATION The general appearance of the automatic apparatus is shown in Figure 3. For aid in description, a diagram of the combined fractionation unit and recording and control mechanism, Figure 4, is presented. COOLING OF REFLUXAND HEATING OF STILL. Liquid air must be admitted to the reflux chamber of the fractionating column in intermittent puffs in such manner as to maintain the column pressure as constant as possible a t the desired value, as indicated on the distillation pressure manome-
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ter. Both the admission of liquid air and the heating of the still must be so conducted that the reflux liquid just wets the column packing wires without excess hold-up. A fine iron or stainless-steel wire, insulated throughout except a t its extreme lower end, is inserted into the open arm of the distillation pressure manometer so that its uninsulated extremity is a few millimeters above the point where mercury will rise at the desired distillation pressure. A return wire is sealed into the manometer near the bottom or inserted through a rubber tubing connection deep into the mercury of the right arm. As soon as the pressure increases sufficiently to cause the mercury of the manometer to make electrical contact with the point of the inserted wire, a circuit is completed through a low-voltage rectifier, through two wire contacts in the mercury, through the mercury, and through a sensitive telephone-type relay. The relay in turn operates a specially designed compact electromagnet valve which permits compressed air to blow liquid air into the reflux cooling vessel from a thermos bottle full of the refrigerant, as illustrated in the diagram. The exact regulation of compressed air admission to the thermos bottle is controlled by a small needle valve, and by a permanent fine Ieak, as illustrated. The introduction of liquid air into the reflux cooling vessel, using the direct cooling tubefi, almost immediately lowers the pressure, whereupon the mercury in the distillation pressure manometer leaves the electrical contact, the relay circuit is broken, and the solenoid valve closes to cut off admission both of compressed air to the thermos bottle and of liquid air to the cooling vessel. Residual pressure in the thermos bottle is immediately dissipated by means of the leak already mentioned. If the supply of liquid air should become exhausted, or the cooling vessel should plug up, or anything else should happen to interfere with the cooling, the column pressure will of course continue to rise in spite of the action of #he automatic mechanism. Eventually the mercury will rise sufficiently to reach the bottom end of another wire to operate a second low-voltage circuit including a buzzer and a trouble signal light labeled “check reflux.” The buzzer will summon the operator, while the light instructs him where to look for the cause of the trouble. The supply of heat to the still may be controlled either manually or automatically. I n manual operation, the operator will check the heat regulation whenever he happens to come to the apparatus and this will usually suffice. The requirement for heat increases normally, and if care be ta#en not to apply too much heat to the column at any time (as may be ascertained by watching the behavior of the liquid streaming down the column packing, for a minute or two) the worst that may happen from operator’s prolonged inattention is a slowing up of effective distillation rate, without any detrimental effect to the accuracy of the results. Insufficient heat supply cannot cause a partial vacuum in the column, because of the functioning of another device described in the following paragraph. For automatic regulation of heat supply a differential manometer connected to top and bottom, respectively, of the distilling tube, is used to actuate a relay which in turn shuts off heat supply to still whenever the pressure drop (proportional to flow of vapor through distilling tube) exceeds a predetermined amount. (This arrangement is not shown in diagram, Figure 4.) CONTROL OF DISTILLATION PRESSURE.The column pressure tends to remain constant, because of the action of the reflux cooling mechanism described in the preceding section. However, it rarely happens that the supply of heat a t the still and the cooling of the reflux balance 80 nicely that there will not be sudden large drops in column pressure or continued partial vacuum. ’Such abnormal conditions, if per-
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INDUSTRIAL AND ENGINEERING CHEMISTRY
mitted, would of course destroy both the sharpness of fractionation and the accuracy of the reflux temperature readings. It has, therefore, been found necessary to insert still another contact wire in the distillation pressure manometer which functions like the other contacts already described, to actuate a relay, whenever the distillation pressure falls about 4 mm. below the distillation pressure. In this case the relay shuts an electromagnet valve in series with the distillate flow line from the fractionating column, thus completely stopping distillation, until the pressure again rises to break contact and to open the valve. In this way column or distillation pressure is forced to stay between adjustable upper and lower limits. The exact adjustment of the various contacts involved is not critical, although certain definite positions for them have been worked out and found to result in smoothest action and greatest economy in the use of refrigerant. The two electromagnet valves for compressed air control and for distillate flow control, respectively, emit different sounds. As a result the operator can actually hear how well and how smoothly the regulatory mechanism is functioning and can immediately detect a wrong note, although he may be concentrating on some other task. This distillation shut-off valve also acts as an accessory to the actual distillation-rate regulating valve described below. In other words, a t breaks, where there is a tendency for column pressure to drop violently, the distillation shutoff valve shuts off the column for fairly long intervals a t a time (because of slow comeback of pressure a t breaks), thus giving the column a chance to fractionate out the last traces of the lower-boiling component remaining in the sample. dT*riMOCo"pIE
~
"TO
IrcDIDw
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Any operator of the low-temperature fractionating apparatus will appreciate that this valve duplicates human operation in this particular function, but more precisely and with 100 per cent dependability. RECORDINQ AND PLOTTING OF BOILINQPOINTAND QUANTITY OF DISTILLATE. The fractional-distillation curve, which summarizes the results obtained by low-temperature fractionation is a plot of two series of observations: (1) reflux temperature and (2) pressure in the initially evacuated system receiving the distillate in vapor form. The ordinary temperature recorder, however, plots temperature against time. It was, therefore, necessary to develop means to operate the chart roller of the instrument in exact proportion to the pressure of the vapor-receiving system. A Bourdontype gage with gear mechanism was not suitable because of its lack of precision and dependability. As will be appreciated by operators of the low-temperature fractionating apparatus, even the enlarged bulb-type barometric manometer used in the Standard Precision model must be read carefully, estimating to tenths of a millimeter, in order to develop the full accuracy of the apparatus. The mechanism finally adopted as most accurate, dependable, and generally satisfactory consists of a combination of (1) a long slender contact rod with its lower extremity almost but not quite touching the mercury in one arm of a special manometer; (2) a special enlarged-bulb large-bore manometer with a gas-tight mercury-seal stuffing box on the arm in which the rod is inserted, and with the enlarged bulb and connection to vapor-receiving system on the other arm; (3) a carriage provided with a split nut to fit around a vertical threaded rod and with a clamp for the slender
LLAOS
OF AUTOMATIC RECORDER AND CONTROL APPARATUS FIGURE4. DIAGRAM
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ANALYTICAL EDITION
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FRACTIONAL-DISTILL4TION ANALYSIS CHART FIGURE5. TYPICAL
contact rod already listed; (4) a low-voltage source and relay circuit completed whenever the contact rod touches the mercury; and (5) an electric motor actuated by the relay when the contact rod touches the mercury and which, through a train of suitable gears and the rotation of the vertical threaded rod in the carriage nut, simultaneously and in exact proportion raises the contact rod and rotates the temperature recorder chart until contact is broken between the contact rod and the mercury. By this action, the contact rod practically floats on the surface of the mercury with barely a 0.1-mm. gap, while the temperature recorder chart unrolls in proportion with the rise of mercury and thus plots the fractional distillation curve with much greater exactness than is possible by the method of manual readings of pressure and temperature. The question of compensation for variation of atmospheric pressure immediately suggests itself, since the manometer used is not of the barometric type. The solution to this problem was found by using a small mercury-seal packing box around the contact rod and by conducting a small tube from this arm of the manometer to a bottle of about 2 gal. (7570 cc.) capacity immersed in a constant-temperature water bath. This bottle is initially opened to the atmosphere before analysis is begun and then shut off. Nitrogen may be used in this part of the system to prevent oxidation of mercury. Since the mercury-seal stuffing box is absolutely gas-tight (1) for moderate pressure differences, the left arm of the manometer will remain a t constant pressure even if the barometer varies 10 mm. or more during the analysis. The capacity of the compensating bottle is made about 2 gal. (7570 cc.), in order to minimize the change in pressure in the bottle due to change of mercury level in the manometer. Finally, it is necessary carefully to calibrate the manometer for nonuniformity of bore and to prepare a chart for correction of the fractional distillation curve both for nonuniformity of bore and for the change in premures of the vaporreceiving system and of the compensating bottle caused by the change of mercury level in the manometer. The correction chart is used only to correct distances between cut points on the finished distillation curve and its use entails little extra labor. It is possible to prepare correction charts for any combination of manometer and volumes of vapor-
receiving bottle system and of compensating bottle, and results corrected with such charts are more accurate than is possible by manual readings and plotting. The chart is made to unroll in the ratio of approximately 1.8 (exact ratio determined by calibration) to the pressure rise in order to give a very open scale on the paper for accurate estimation of cut points (Figure 5 ) . It should be noted that the abrupt drops in temperature in the butane plateau and beyond are due to lowering of distillation pressure in the usual manner. It has not been found necessary to introduce any device for automatically correcting temperatures for pressure, as the chart can be interpreted without such correction. Reevacuations are indicated on the chart by long inked lines perpendicular to the pressure axis and followed either by resumption of the plateau or by an abrupt shift of temperature due to change of pressure as just explained. DISTILLATION RATECONTROL.I n the development of an automatic recording and control apparatus, considerable difficulty was experienced in solving the problem of regulating the distillation rate in approximately inverse proportion to the tendency of the temperature to rise. I n other words, according to well-known fractional distillation theory and experience, the rate of distillation should be approximately inversely proportional to the instantaneous tangent of the fractional-distillation curve at any point. (In the case of this apparatus, distillation rate is inversely proportional to reflux ratio.) The manual operator solves the problem by changing the distillation rate in steps (8), and his greatest exercise of skill and judgment consists in the way he makes these changes to get the sharpest breaks in least total time for the distillation. It was found necessary to develop both a special externally leakproof very small capacity regulating needle valve and an electrical contact follow-up device to take motion off the temperature-indicating parts of the recorder and to correlate this motion with the motion of the mechanism already described for unrolling the chart roll in such manner that the regulating valve would open (and close) inversely as the tangent of the fractional distillation curve. I n order to be able conveniently and in a practical manner to take motion off the temperature-indicating parts, the recorder must necessarily be of the potentiometer type rather than the millivoltmeter type. I n the case of the Brown
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RECORD SECURED BY AUTONATIC OPERATION AND RECORDING potentiometer recorder, the spiral pen shaft indicated in the diagram revolves in exact accordance with the rise of temperature. Onto this shaft is therefore fastened an electrical contact follow-up device, very similar to the chartrolling mechanism already described in that a relay-actuated motor simultaneously keeps the follow-up (more properly, run-away) contact piece out of electrical contact and also operates proportionately one end of a device called the “tangentor.” The other end of the tangentor is actuated by the chart-rolling motor. The tangentor itself is simply a male-threaded member engaging a corresponding femalethreaded member, both constructed so that the male member can travel only a limited distance either upward or downward before it slips out of threads and simply rotates until the relative direction of motion of the two parts is reversed, when the threaded parts again engage. It will be noted that, essentially, the tangentor takes motion a t one end corresponding to the rise of pressure in the vapor-receiving system; while at the other end it takes motion corresponding to the rise of temperature in the reflux. Depending upon the relative speed of rotation of the two motions, the male member of the tangentor moves up or down within its limits of travel, simultaneously opening or closing the regulating needle valve through the means of an arm and fulcrum arrangement. In other words, the opening of the valve is inversely proportional to the tangent of the distillation curve. A sharp rise in the fractional distillation curve, as it is being continuously and instantaneously plotted on the chart, almost immediately closes the valve. A small rise begins to close the valve. When the curve flattens out, the valve opens gradually. The regulation is truly proportional and may be made as sensitive as desired by the use of suitable gear ratios. It is obvious that the distillation rate cannot be permitted to become zero a t any point or the distillation would stop permanently a t that point. Therefore, a micrometer adjustment is provided on the valve stem for the exact setting of a definite low rate to provide a minimal flow of distillate at breaks no matter how sharp. Also, there must be some means of regulating the maximum opening of the valve a t plateaus; otherwise the capacity of the column might be exceeded. This requirement is met by a variable fulcrum on the arm connecting the tangentor and valve. These
adjustments need be changed only when the distillation pressure is changed and to secure different degrees of accuracy or different total times of distillation. The regulating valve must necessarily be made with great precision. The needle is of the actual dimensions of a medium-sized sewing needle with a seat of corresponding dimensions. I n order to compensate completely for the disturbing force developed through difference in atmospheric pressure and in the pressure of the vapor receiving system, two flexible metallic bellows are incorporated in the valve construction as shown. The regulating valve is in series and immediately connected with the electromagnet shut-off valve. I n order to assist in the adjustment of the regulating valve and also to have a complete record of the functioning of the regulating means and of the entire automatic apparatus, an auxiliary pen on the recorder (towards the right of the chart) is made to jog every 75 seconds through a gear and cam mechanism operated by the recorder motor, as shown in Figure 4. This curve (Figure 5 ) shows the remarkably sensitive and more than human response of the regulating valve to every slight wiggle of the reflux temperature. Certain noncontinuous functions, such as the actual entering of the sample, change of distillation pressure, reevacuation of distillate receiver, use of fraction-collecting burets, etc., cannot be made completely automatic without undue complication of apparatus. Automatic signals are therefore incorporated in the apparatus so as completely to free the human operator from the necessity of attending the apparatus until the robot operator summons him by a loud buzz and then further indicates the reason for the summons. The signals used are the following, as indicated over the corresponding trouble lights: REDUCEDISTILLATION PRESSURE.When reflux tem erature a proaches room temperature, an electrical contact on t i e frame orthe recorder operates to sound the buzzer and to light the red trouble light bearing the label as stated. REEVACUATE. When the pressure in the vapor-receiving system reaches the maximum permissible for the hydrocarbon distilled, or when it ap roaches distillation pressure, an electrical contact device locatel on the smooth guide rod next to the threaded rod is actuated by the rise of the contact rod carriage to sound the warning buzzer and to light another red trouble light. CHECKREFLUX. This signal summons the operator when, for any reason, the cooling of the reflux becomes imperative.
ANALYTICAL EDITION
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DISCUSSION Figure 5 illustrates the results secured with automatic operation in the analysis of a natural gas. The presence of air or nitrogen is evidenced by the unduly low temperature and disturbances in the first portion of the methane plateau. The distillation rate or jog curve indicates the extremely sensitive and truly proportional regulation of distillation rate effected by the automatic control. As a result, the breaks of the curve are extremely sharp, considering that the curve is plotted on a pressure scale almost double the actual pressure rise. The chart itself is a standard 12-inch roll chart available for use with the Brown potentiometer recorder. (The recorder itself has been considerably modified.) Similarly, sharp curves may be secured for the distillation of natural gasoline, motor fuel, absorption oil, or other samples suitable for analysis in the low-temperature fractionating apparatus. The automatic apparatus is inherently more positive and accurate than the human operator, as shown in Table I which gives a comparison of various analyses run in duplicate both by the robot and by a skilled human operator. TABLEI. TYPICALCHECKANALYSESWITH AUTOMATIC CONTROL AND RECORDINQ APPARATUS Methane and lighter Ethane Propane Isobutane n-Butane Pentanes Hexanes and heavier
AUTOMATIC OPERATION First run Second run 64.99 64.95 16.53 16.60 11.44 11.53 1.14 1.18 2.93 3.05 ::;:]2.81 ::!:]2.85]
100.00
100.00
MANUAL OPERATION 65.1 16.7 11.5 1.0
..
2.8
100.0
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controlling apparatus, with the assurance that the operation will give him a near approach to the best results possible for the particular fractionating unit and for the total distillation time used. The printed curve chart is unbiased, includes a check on the functioning of the distillation control in the form of a distillation time rate curve, and is in ideal form for inspection and criticism and for future reference. The curve is a complete record of the distillation and even reveals the possible poor functioning of the automat due to improper adjustments, leaks, or other troubles. Analyses run on the same sample in different laboratories by different operators but with the same apparatus and main adjustments should yield practically identical curves and results. It remains to consider the standardization of decisions and functions not taken care of by the automatic apparatus which may be listed as follows: 1. Design of fractionating unit proper 2. Size of sample 3. Entering sample
Completing distillation 5. Automatic adjustments u. Contacts in distillation pressure manometer b. Distillation regulating valve adjustments c. Compressed air needle-valve adjustment 6. Choice of distilling tube and bulb on fractionating column of distillation unit 7. Manidation of mercurv seal and suuulv - _ - of heat to distilling bulb 8. General preparation and maintenance of distillation unit, involving evacuation, checking for leaks, cleaning, greasing stopcocks, etc. 9. General preparation and maintenance of automatic recording and control unit involving cleaning- contacts, oiling and greasing when required, servicing etc. 10. Miscellaneous 4.
A
The saving of time on the part of the operator using autoFractionating unit design (1) has been discussed above. matic operation is very material. During its period of opera- Any instrument, whether automatic or not, will require such tion, the apparatus is from 80 to 90 per cent automatic, and preparation and care as are outlined in (8) and (9). The the operator is free to do other work so long as he is within comparatively simple functions (3), (4), and (7) are readily hailing distance of the automatic operator. The automatic standardized, and (2), ( 5 ) , and (6) may be standardized by apparatus plots the complete distillation curve in finished the preparation and use of a suitable standardization chart, form and thereby saves the operator about an hour’s time taking into account the accuracy required, total time of disin plotting his readings and drawing the distillation curve. tillation, etc. In this way substantially complete standardiAutomatic operation is inherently more efficient, so that zation of the low-temperature fractionating apparatus and its the total time of distillation required to get results of any operation may be effected. required accuracy is decreased considerably over that possible with even the most skilled human operation. For ACKNOWLEDGMENT similar reasons the consumption of liquid air is reduced 15 Grateful acknowledgment is made to the Brown Instruto 20 per cent. ment Company for the use of a Brown potentiometer recorder In spite of the number and complexity of the functions it during the period of experimentation and for whole-hearted performs, the automatic apparatus is neither a very compli- cooperation on the adaptation of the instrument to this cated nor a delicate mechanism. The component parts purpose. (except the potentiometer recorder) are mostly gears, bearings, electric motors, telephone-type relays, etc., which in LITERATURE CITED themselves are sturdy and not likely to cause trouble. The (1) Brown, Proc. Natural Gasoline Assoc., 7th Convention, p. 53 (1928). needle-regulating valve is not subject to action which would (2) Podbielniak, IND. &a. CHEM.,Anal. Ed.,3, 181 (1931). tend to damage it in any way. The electromagnet valves (3) Ibid., 5, 119 (1933). are of very simple construction. Leaks must of course not September 15, 1932. Presented before the Division of Petroleum be present, as they would destroy the accuracy of the ap- RECEIVED at the 84th Meeting of the American Chemical Society, Denver. paratus. However, the presence of leaks would be indicated Chemistry Colo., August 22 to 26. 1932. on the plotted distillation curve. The practical usefulness of automatic operation would be considerably diminished if more trouble developed through it than naturally occurs WOOLINTERESTS of Bradford, England, are carrying on extenwith the distillation unit, but experience in the author’s sive research work to develop a container for raw wool to replace laboratory has shown that this possibility is not an actual jute sacks, according to the Commerce Department. one. Wool manufacturers are said to object to certain features of INFLUENCE ON STAKDARDIZATION. The automatic re- the jute bag, among them the alleged tendency of jute particles to work loose and mix with the wool. The latest experiments cording and control apparatus represents a standardization concern a paper-yarn container. Rags made from this material of factor 3 (3) for low-temperature fractionations. The have the appearance of canvas. The wood pulp is said to be operator merely decides approximately what total time of available in unlimited quantities in Russia and the Scandinavian distillation he desires and fixes a few adjustments on the countries.
