ANALYTICAL EDITION
May, 1946
ing that the heater is not under the control of the regulator. After the water has warmed sufficiently t o close the regulator contacts (20 t o 30 minutes with the unit now in use), the by-pass switch is thrown to position 2 and Sais closed momentarily. Pilot light Pp now burns t o show that the heater is controlled by the regulator. T h e temperature drop due t o the change from liquid t o gas phase a t the thermoregulator bulb as the reservoir empties causes the regulator contacts t o open. This break in the secondary circuit immediately opens t’he relay and shuts off t,he heater and primary coil of the transformer; thus, continued arcing a t the regulator points and relay chatt’er, which are common when alternating current is used with mercury regulators, are eliminated. It is not possible to’turn the heater on again until the relay is reset, eit,her manually or electrically. The control system can be somewhat simplified as follows: T h e primary coil of the transformer can be wired directly to the line switch, Si, instead of t o the relay as shown in Figure 2. (The heater must, of course, remain wired to the relay as shown in Figure 2.) T h e primary coil of the transformer is then energized whenever SIis closed. S3 can then be replaced by a doorbell-type push button in parallel with the secondary pole of the relay. Signal transformers are designed for continuous dut!, iind
A
333
it, does no harm if the primary of the transformer remains energized after the heater is turned off. S , can be a shortingsmitch (“make before break”) instead of one of the common toggle type. Such a switch would eliminate the necessity for resetting the relay after changing the position of 8,. The signal lights can be eliminated. T h e thermoregulator is then connected directly t o the coil of the relay and a single-pole single-throw t,oggle switch is placed in parallel with the thermoregulator. The sn-itch is “on” during the preliminary warm-up and “off” after contact is made a t the thermoregulator. T h e entire cost of materials listed under Figure 2, exclusive These makes, types, and capacities were used because they were immediately available. Other materials of similar characteristics could have bcen used. This device should find use in other applications where change in level of a liquid results in lowered temperat’ure.
of the thermoregulator and the heat,er, is about $9.
LITERATURE CITED
(1) Holmes, F. E,, ISD. ENG.CHEM.,A N ~ LED., . 12, 483 (1940).
Reaction of Lead Soaps with Sodium Iodide ROBERT S. BARNETT, The Texas Company, Beacon, N. Y.
P
REVIOUS investigators (1, 4-71 have slroivn that reactions of the double-decomposition type can take place in insulating
solvents such as dry benzene between heavy metal soaps and dry hydrogen chloride or metallic chlorides, >uch as stannic chloride, rvhich are also soluble in benzene. T h e present communication summarizes preliminary Tvork which has been done to apply a reaction of lead soap with sodium iodide to the development of a suitable method for determining free organic acids in lead soaps. The essence of a n analytical niethod is presented, and seniiquantitative data, obtained on lead soaps made from organic acids of differing molecular weights, are given. I n attempting to develop a method for the determination of free organic acids in lead soap it was found that the addition of an acetone solution of sodium iodide to a n acetone-benzene solution of lead soap apparently causes a douhlc-decomposition reaction a? follom: 1,ead soap
+ Sa1
--f
a lead iodide
+ sodium soap
The mixture turns a bright greenish yellou. upon addition of t h e sodium iodide solution and Aocs of soapy-looking material ,separate out when the solvents are evaporated t o dryness. The rrridue after evaporation is bright yellow, and gives a n opalesc n i t , frothy, Boapy extract with water, which is alkaline to phenolphthalein and gives a curdy precipitate with barium chloride solution ( 3 ) . S o lead \vas found in the benzene extracts from five dried residues extracted individually. This indicates that all the benzene-soluble lead soap had been converted t o a txsiizene-insoluble lead iodide, possibly a basic iodide. Both commercial lead oleate and lead naphthenates have been trvated in solution with sodium iodide Tyith the same general re.*ults, the sodium oleate formed separating out more quickly upon solvent evaporation than the sodium naphthenate-i.e., seeming to be more insoluble in these solvents, as would be expected. Warm 95T0acetone (5% water) is a n excellent solvent for extracting organic acids, including oxidized fatty acids, from lead soap or lead soap lubricants. However, a small amount of lead soap is dissolved concurrently, which invalidates the usual titration for free organic acids of the combined acetone extracts, because the heavy metal soap is titrated as free acidity ( 2 ) . Some work has been done in using the foregoing lead soapsodium iodide reaction t o transform such dissolved lead soap in combined acetone extracts t o sodium soap and a lead iodide. By extrarting the dried residue left after evaporation of the acetone
with hot benzene it is possible to isolate the free organic acids (together with a small amount of sodium soap), leaving behind the lead iodide, excess sodium iodide, and most of the sodium soap. The extracted material taken up in alcohol can then be titrated forfree organic acids in the usual manner, as the sodiumsoap present does not interfere. Semiquantitative results for free acids on lead naphthenates made from naphthenic acids of different molecular weights, using the above technique, indicate a much higher free acid content for the soap made from high molecular weight acids, the following comparative figures being obtained: Lead Soap From 176 saoonification value acids (318 calculated hole&lar weight) From 282 saponification value acids (199 calculated mdecular weight)
0rg.anically % Free F a t t y Combined P b Acids a8 Oleic 18 5
10
41 3
3
The greater reactivity of the lower molecular weight acids with lead may account for the lower fr Indications hare also been obtained that sodium iodide in acetone solution does not react with lead oxide (which may be present in lead soaps) to give free caustic alkali, which would, of (‘ourse, invalidate the determination of free acidity. However, this reaction does occur when lead oxide is heatcd with aqueous sodium iodide solution. It is proposed for the future to ascertain by analysis whether the lead iodide compound formed is a basic salt or the normal diiodide, and thus gain some idea of the structure of the dissolved lead soap. It is also proposed t o complete work on the analysis of lead soap5 containing weighed additions of free organic acids, ubing the technique described above, in order t o define the accuracy and reproducibility of this method as a means of determining free organic acids in lead soaps. LITERATURE CITED
Allen, H. C.. “Instantaneous Chemical Reactioiia in Benzene and Toluene”, Kansas Univ. Sci. Bulletin, 1906. Am. Soc. Testing Materials, Committee D-2, p. 187, Section 20 (b), Methods of Analysis of Grease (D128-40), A.S.T.M. Standards on Petroleum Products and Lubricants (September, 1945). Barnett, R. S., IKD.ENG.C m x , ANAL.ED.,7,183 (1936). Cady, H. P., and Baldwin, E. J., J . Am. Chem. SOC.,43, 646 (1921). Cady, H. P., and Lichtenwalter, H. O., Ibid., 35,1434 (1913). Kahlenberg et al., J . Phys. Chem., 6, 1 (1902). Koenig. .A. E.. J . Ani. C‘hem. SOC., 36, 951 (1914).
