478
INDUSTRIAL AND ENGINEERI.VG CHEMISTRY
Saybolt viscosity readings supplied with the instrument in Figure 8. On the top side of the scale the viscosities of less than 180 seconds were graduated in zones such as “Poor” and “Dangerous.” To show more clearly how these instruments record what actually is taking place and to what extent the lubricant is contaminated, the tabulation of cars drained a t several service stations during the same day is recorded in Table I. Such devices allow the motorist to determine when his niotor oil is getting badly contaminated and so light in body
Vol. 17, s o . 5
that it is not giving the proper piston seal. They also tell him that his fuel mixture is incorrect, that he is using choker too freely, or that the grade of fuel he is using accentuates dilution. The factors entering into this dilution problem are so numerous that the present stated period of draining the crank case does not remedy the situation. In draining the oil a t predetermined periods, it is discovered either that the oil is past the point of suitability or that it still contains sufficient body to lubricate properly, and therefore should not be thrown away.
Comparison of Monel and Copper Kettles in Boiling Linseed Oil’ By C. Fichandler REPCBLIC VARNISHCO.,N E W . 4 R K , N. J
T
HIS investigation was undertaken in order to determine palest oil, several shades lighter than that cooked in the copthe effect of the material of which a varnish kettle is per pot, while the iron pot developed by far the darkest oil. made on the properties of a kettle-bodied linseed oil. This investigation was criticized by Harrison’s colleagues, The color of the finished product is of primary importance to however, on the ground that laboratory results frequently the paint man since the whiteness of a high-grade enamel prove a t variance with results on a commercial scale, and is a function of the paleness that he had neglected to of the bodied oil. The correlate his color changes effect of the kettle reactions with any of the chemical reLinseed oil “heat-bodied” in a monel metal kettle on the acidity of the oil is of actions of the oil. It was in is found to be paler in color and to have a lower acid equal i m p o r t a n c e . T o o an effort to meet this critivalue than that cooked in a copper kettle. This is due high a percentage of free cism that the present work to the fact that copper is not so resistant to attack acids in an oil will cause it to was undertaken. It was by the free acids of the linseed oil as is monel metal. “body up” or even “liver,” carried on under typical The soluble copper soaps formed cause a darkening of when brought into contact factory conditions so that the oil and also tend to increase the rate of formation with highly basic pigments data of value to the pracof free acids. such as lead or zinc. This tical varnish man might be This was determined by bodying batches of linseed is due to the formation of obtained. oil in monel and copper kettles under identical heat metallic salts or soaps2 of conditions. Samples were withdrawn from both at Operation the free fatty acids. These definite intervals, and viscosity, acid number, iodine d monel metal set-kettle soaps are insoluble in the oil number, and color were thus determined at each stage of about 500 gallon capacvehicle and are dispersed of the operation. ity was compared with an through it as a colloid, ordinary 150-gallon copper thereby increasing the invarnish kettle. ternal surface of the mix(It was impossible to compare kettles of the same size as ture, with a resultant increase in the body of the paint. Thus, oils of high acidity tend to produce enamels which a t the time of the experiment the plant was equipped with become thick and pasty, with a loss of the desired brush- only the large type of monel kettle.) A batch of 300 gallons of oil was cooked in the former while the latter held 75 gallons. ing and flowing qualities. In view of these facts it is indeed surprising that very little The size of the batches was so selected that the ratio of the systematic study has been conducted on the relation of the mass of the oil to the area of the surface exposed to the air varnish kettle to the production of a pale, low-acid bodied oil. was approximately the same. Thus the factors that might Although the varnish-maker has found that kettles of copper operate in darkening the oils through oxidation were made produce a paler oil than those of steel, there are practically no identical in both kettles. Heat was applied to both kettles a t the same time and temdata on the subject in the literature. However, a very interesting piece of work was carried on by peratures were observed every half hour. By regulating the Harrison3in an attempt to determine the effect of aluminium, kerosene burner that was heating the copper kettle, and by copper, and iron kettles on the color of bodied linseed oil. removing the kettle from the fire when necessary, it was posHe obtained three set-pots of about a half gallon capacity and sible practically to duplicate the temperature-time curve of bodied quart batches of oil a t 610” F. in each set-pot. He the larger set kettle. I n this way both masses of oil were then compared the color of the finished oils by simple ocular cooked under the same conditions; thus any variation in the comparison and by means of a Lovibond tintometer, record- characteristics of the finished oil could then be ascribed to the ing the relative darkness of his oils in terms of the number of composition of the kettles, rather than to viscosity differunits of yellow developed. After several determinations, he ences caused by variations in heat treatment. In 4 hours the oils reached the temperature range a t which proved conclusively that the aluminium pot developed the polymerizaton takes place (570” to 600” F.), and samples 1 Received November 7, 1924. of each oil were withdrawn. Thereafter samples were taken * Pickard, Am. Paint J . , April 10, 1922. every hour for 5 hours. a Harrison, Proc. Paint Varnish SOC.,1920.
INDUSTRIAL AND ENGINEERING CHEMISTRY
May, 1925
The kettle reactions of bhe oils were next ascertained by examination of the samples that had been withdrawn a t different stages of the polymerization. The color, viscosity, acid number, and iodine number of each sample were determined. The viscosity was determined by mixing 60 grams of oil with 30 grams of redistilled spirits of turpentine and noting t,he time necessary for 90 cc. of this mixture to run through a viscometer of the flow type a t 70" F. The color was observed by placing the oils in small tubes of the same bore and examining them by transmitted light. The acid number was determined by refluxing 2 to 4 grams of oil in 50 cc. of a neutral benzol-alcohol mixture for a half hour and then titrating against a decinormal solution of sodium hydroxide. The iodine number was determined by the Hanus method, keeping 50 to 60 per cent of Hanus solution in excess in each absorption. The oil used was an alkali-refined oil and gave the following analysis :
479
The relatively darker color of the samples taken from the copper kettle has been interpreted in two conflicting ways. The natural assumption is that the free acids in the oil attack the metal kettle, forming soluble metallic soaps which tend to darken the finished oils. Thus, iron soaps would discolor oil more than copper and copper more than aluminium. Reid,3however, claims that in examination of oil boiled in a steel kettle he was able to find scarcely a trace of iron. Discarding the solubility theory, he asserts that the catalytic action of the metal in contact with the oil in the presence of air causes considerable oxidation followed by appreciable darkening of the oil. He explains the fact that some kettles yield darker oils than others by the relative catalytic strength of iron, copper, and aluminium in that order.
Specific g r a v i t y , . . . . . . . . . . . . . . . . . . . . 0 . 9 3 3 Iodine number (Hanus), . . . . . . . . . . . . . 1 8 0 . 2 0.92 Acid number.. . . . . . . . . . . . . . . . . . .7. 10 seconds Viscosity.. . . . . . . . . . . . . . . . . . . . . . . . . .
Data Time 6.45 7.15 7.45 8.15
x- . 4.5 --
9.15 9.45 10.15 10.45 11.15 11.46 12.15 12.45 1.15 1 45 2.15 2.45 3 15 3.45
TEMPERATUREVISCOSITY ACIDNCXBER F. SECONDS IODINENUMBER Mc. Monel Copper Monel Copper Monel Copper >lone1 Copper .. .. Start Stait 10 10 1 8 0 . 2 180 2 0.92 0.92 170 220 235 285 300 300
-x-m-
455 526
572 570 585 589 588
587 575
585 576
580 580 530
I
I
1
1
3
m- - x-
450 525 580 575 587 588 588 587
5
6
7
8
9
Time (hours) 11
11
165.6
166.5
1.71
1.69
14
15
154.0
153.2
3.58
3.7
19
20
144,O
144.2
5,s
6.35
577 580 570
29
30
137.0
137.5
7.75
9.35
46
48
134.6
134.0
9.2
66
134.1
134.0
10.6
515
64 73
575 575
4
74
11.3
11.1 13.05 14.5
.4t every stage of the operation the oils withdrawn from the copper kettle were noticeably darker than the corresponding samples from the monel batch. Discussion of Data
The viscosity curves (Figure 1) show that the control of the heat conditions of the two batches was successful. The viscosity of both oils was practically the same a t every stage of the Operation, indicating that polymerization took place a t the same rate in both kettles. Hence, any variatims in the other chemical properties of the oils cannot be laid to any variations in the heat treatment of the two batches, but are due solely to the reactions of the kettle surfaces with the oils. The iodine number curves (Figure 2) show that the rate of polymerization and oxidation of the unsaturated glycerides \vas unaffected by the composition of the kettle. Nevertheless, the results were of interest as a check on the control of the operation. The iodine number of an oil varies inversely with the viscosity or degree of polymerization. Hence, the close agreement of the results a t practically every stage of the operation furnishes additional evidence that heat conditions in both kettles were identical. Of purely theoretical interest is the rate of change of the iodine number. In reaching 580" F. it dropped 14 points, falling off only 9 points in the next hour, and dropping still less in the ensuing time. This would indicate that the polymerization of the more highly unsaturated linolenin with three double bonds, and linolin with two, begins quite early in the heating process and proceeds rapidly till most of their linkages have been closed. From then on, polymerization of the less unsaturated olein is much less rapid.
Figure 1
Xevertheless, the weight of evidence seems to point to the solubility explanation mentioned previously. Gardner4 has recently conducted some valuable experiments on the availability of various metals and alloys for use in constructing varnish kettles. On immersing strips of metal of approximately 4.5 square inches surface area in high-acid linseed oil a t 500" F. for 2 hours, he found that the resistance of monel metal to the fatty acids of linseed oil was considerably greater, than that of copper. On reweighing a strip of monel metal originally weighing 21 grams, he found that its loss in weight was 0.0003 gram, whereas a strip of copper weighing 19 grams lost 0.0006 gram, exactly twice as much under identical conditions.
1
2
3
4
5
6
7
6
lime (hours) Figure 2
This bears out the theory that the relative darkening of the copper-boiled oil can be ascribed directly to the presence of dissolved copper in the form of soluble soaps, whereas a very much smaller amount of metal went into solution from the monel kettle. Still further evidence in favor of this explanation will be found on considering the curves on acid numbers. Linseed oil is composed of glycerides of linolenic and linolic acids, with smaller amounts of oleic and stearic acids. Prac4
Gardner, Paint Mfrs. Assoc., Circ. 146 (May, 1921).
ILt'DL'STRIdL A S D ENGINEERING CHEMISTRY
480
tically all treatments, such as aging, oxidation, and polymerization, bring about a splitting of these fatty acids from the glycerol. Thus it is seen that the acid numbers of both oils increase as the polymerization advances. This is explained by Coffey5as due to the hydrolysis of the glycerides by water, traces of which are to be found in raw linseed oil.
/ OLn C3H5-OL \ OSt
Yol. 17, No. 5
feet. Hence the higher acidity of the oil boiled in contact with copper offers indirect but positive evidence that the concentration of metallic catalysts therein was higher than in the monel
+ ~ H Z O - Glycerol C~H~O+ H ) HLn ~ + HL + HSt Linolenic Linolic Stearic acid
acid
acid
At the high heats reached the glycerol is rapidly volatilized, so that, following the mass law, the reaction goes on towards completion. Moreover, the glycerol is continually being broken up into acrolein and water; the constant formation of the latter also aids in pushing the reaction towards the right. The significant feature of the acid number curves (Figure 3) is the gradually increasing differenceor spread between the oils from the copper and monel kettleswhich had been bodiedunder identical conditions. At first the amount of free acids in both oils seems about equal, but as the operation continues the increase in therate of formation of free acids in the copper kettle grows larger and larger than the corresponding increase in the monel batch. At the end of a constant increase the copper-boiled oil has an acid number 3.2 mg. higher than the monel-boiled oil. It is known that metallic soaps2of any kind will catalyze the acid-forming reaction described above, and that the rapidity of formation of free acids is proportional to the concentration of metallic soaps in the oil. Even minute quantities, too small to be detected by direct analysis, exert an appreciable ef6 J . Soc Chem I d , 40, 19 (1921).
1
2
3
4
5
6
7
8
9
Time (hours) Figure 3
heated oil. Thus the acid number curves also tend to show that the relative darkness of oil bodied in the copper kettle is due to the presence of an excess of copper soaps, resulting from the relative solubility of copper in the free acids of linseed oil. Conclusion
In the production of a kettle-bodied linseed oil, varnish kettles of monel metal have been found superior to copper kettles in two respects: (a) a much paler oil is produced; (b) a lower acid product is formed, because copper is more soluble in the acids of linseed oil than is monel metal.
Large-Scale Preparation of Sodium Amalgam i n the Laboratory' By R. R. Read and Carl Lucarini U N I V E R S I T Y O F VERMONT, BURLINGTON, VI'.
HE usual method of preparing sodium amalgams by the addition of sodium to mercury is a laborious one and requires the observance of cautione2 In the preparation of small quantities of low-concentration amalgams the expedient3 of melting the sodium under toluene or xylene and adding the mercury slowly suggested the method described herein for the preparation of amalgams of all concentrations in quantities of 15 kg. or less. The top is cut from a steel mercury flask in a lathe and two holes are bored in it. One is tappedfor a length of 6.4-mm. (l/r-inch) pipe, closed a t the lower end, which serves as a thermometer well and stirring rod. The required amount of sodium is placed in the flask, the top set in place, and 25 cc. of toluene are added through a funnel in the second hole in the top. The flask is then heated until the sodium is melted and the mercury added slowly. During the early stages of the addition there may be bursts of flame, or even slight explosions, but these do not lift the top off the flask. More toluene may be added to prevent oxidation. Some mercury vapor is undoubtedly thrown out of the flask, so that a well ventilated hood is necessary. The latter portions of the mercury may be added rapidly. When the amalgam is completely melted, it is stirred and poured into a round-bottom kettle to cool. Amalgams up to 3 per cent of sodium may be granulated 1 Received January 28, 1926. 2
A complete melting point curve for sodium amalgams is given by
Van Stone, Chem. News, 108, 181 (1911). a Net, Ann., 380, 307 (1891).
by vigorous stirring during cooling, the few remaining lumps being crushed with a pestle. This is particularly successful with 2 per cent amalgams. A useful modification is that of pouring the molten material into t ~ l u e n e but , ~ the writers have not found it adaptable to large quantities. To prevent ignition, amalgams of 15 to 25 per cent sodium are best poured after the addition of mineral oil. This can be washed off with toluene, care being taken to open up any oil pockets. The solid amalgam may be crushed in a power-driven jaw crusher or in a large iron mortar by hand. In either case a moist gauze bandage should be worn over the face as the inhalation of the dust may cause pronounced symptoms of mercury poisoning. The crushed material heats rapidly on exposure and should be covered immediately. One melt, exclusive of crushing, may be completed per hour. If it is desired to avoid the possible contamination from the iron vessels, smaller quantities of low concentration amalgam may be prepared in glass.2 As much as 4 kg. of 2 per cent material may be prepared a t once. The sodium is melted down under the toluene on an electric hot plate in a Pyrex beaker, chosen for its unusual thickness and the mercury added with caution. The material may solidify. In such a case, after all the mercury has been added the beaker is heated until the toluene has boiled away and the amalgam becomes liquid. The dross is removed and the melt cooled with stirring, the product being finely granular. The time required is about 3.5 hours. Hirschfelder and Hart, THISJ O V R N A L , 12, 499 11920).
*
