V O L U M E 25, NO. 2, F E B R U A R Y 1 9 5 3
349 have fallen into receiver 15 for a t least 5 minutes. Turn on Powerstat 1 to a voltage high enough to heat the column and tubes to about the boiling point of toluene and continue to distill until the water in the condenser jacket has boiled for a t least 15 minutes. Turn off both Poiverstats. Read the volume on the watermethanol buret and titrate the excess Karl Fischer reagent in receiver 15 to a dead-stop end point. Reread the water-methanol buret to determine the volume used.
_1
Calculation. ( A ~
x
B
- c x D )100 = E
%H,O
where A = ml. of Karl Fischer reagent B = Karl Fischer reagent factor, grams of water per ml. = ml. of water-methanol solution D = water-methanol solution factor, grams of water per ml. E = weight of sample, grams
c
DISCUSSlON
Figure 1. Apparatus 1, 2.
3. 4. 5. 6. 7. 8. 9. 10.
11. 12.
13. 14.
15. 16. 17. 18.
18. 20.
Powerstats Distilling flask, I-liter Heating mantle, Glas Col Weighing-dropping funnel Fractionation column, length 25 inches diameter 15 mm. Glass helix packing, I/r-inch diameter ;urns Asbestos insulation Heating tape Water-methanol solution reservoir, capacity 2 liters Water-methanol solution buret, capacity 50 ml. Drying, tube, CaCh Karl Fischer reagent reservoir, capacity 2 liters CaC12 receiver vent Flask 500-ml., round-bottomed, 3-necked, electrode joint, vent Bbtldurn wire electrodes M a netic stirrer KaA Fischer reagent buret, capacity 50 ml. Condenser Ground-glass standard-taper connection
The sample container is attached to the distillation flask by means of a standard-taper joint which facilitates weighing and interchanging of containers. DETERMINATION
Pour 500 MI. of toluene through 8 25-Inch tower 20 mm. in diameter, filled with 8-mesh activated alumina, into distillation flask 3. If the apparatus has been used previously, this step may be eliminated by reusing the old solvent. Should the distillation flask and receiver be too full, they may be easily emptied by siphoning, Fill separatory funnel 5 x-ith sample [for grease samples the Roberts and Levin ( 2 )grease sampler is convenient], weigh, and insert in the standard-taper joint, 20, in place of the tower. Through the electrode glass joint in receiver flask 15, pour 25 ml. of dry methanol. Replace the electrode firmly. Turn on Mag-Mix, 17, and add an excess of Karl Fischer reagent from automatic buret, 18, until the “dead stop” potentiometer needle is permanently deflected to a reading of a t least 40 pa. if a micioammeter is used as the current-measuring device ( 1 ) . Turn on Powerstat 2, connected to heat distillation flask 3, and set the voltage sufficiently high to distill the liquid into the flask rapidly (1 or 2 drops per second). Heat until drops have distilled into receiver flask 15 for 5 minutes, then turn on Powerstat 1 to a voltage high enough to heat the connecting tubes to about the boiling point of toluene, and continue distilling for a t least 15 minutes or until the water in the condenser jacket, 19, has boiled a t least 10 minutes. Turn off Powerstat 1 and reduce the voltage of Powerstat 2 just low enough to stop distillation in flask 3. If all the Karl Fischer reagent has reacted, add more and continue the distillation until none is consumed by further distillation, then titrate the excess to a dead-stop end point ( 1 ) with water-methanol from automatic buret 11. When the end point has been reached read the volume of the Karl Fischer buret, add approximately 10 ml. in excess of the amount expected to react with the water to be distilled from the sample, and reread to determine the exact volume added. Open the stopcock in separatory funnel 5 , remove the glass stopper, and allow the sample to flow into distillation flask 3. Close the stopcock and replace stopper when the funnel has emptied. Viscous liquids may be added in this manner, as the weights are determined by difference. Raise Powerstat 2 sufficiently to start rapid distillation (one or two drops per second) and allow to distill until drops of distillate
The choice of solvent or azeotrope Eormer for use in this method was mentioned by Roberts and Levin ( 2 ) . However, for very small amounts of moisture it is very necessary that a highly efficient azeotrope former be employed. The writers found that in most cases toluene was more efficient and more easily dried than benzene. I t is miscible nTith most of the same substances as benzene, and forms an azeotrope with water which contains 13.5% water and boils a t 84.1 C. (the benzene azeotrope contains 8.8% water and boils a t 69.1” C.). Toluene boils at 110.6’ C. This is a sufficiently high temperature to prevent sorption of water on the walls of the apparatus. If the sample is not soluble in toluene or benzene, it will be necessary to employ a more suitable solvent. Roberts and Levin (2) used pyridine successfully with greases. ACKNOWLEDGMENT
The authors wish to express their appreciaticn to Davenport Guerry and J. F. Santrock for their suggestions regarding design of this apparatus. LITERATURE CITED (1) Foulk, C. W.,
and Bawden, A. T., J . Am. Chem. Soc., 48, 2045
(1926). (2) Roberts, F. M., and Levin, H., ANAL. CHEhf., 21, 1553 (1949), RtcEivED
f o r review August 16, 1952.
Bccepted September 30, 1962.
CORRECTIONS Isolation of Olefins from Bradford Crude Oil K. van Xes has called attention to an article entitled “Olefinic Components of a Pennsylvania Crude Oil” [Haak, F. A., and van Xes, K., J. Inst. Petroleum, 37, 245-54 (1951)], which should have been mentioned in my article entitled “Isolation of Olefins from Bradford Crude Oil” [ANAL.CHEM.,24, 1551 (1952)]. The oversight is regretted. I had every intention to include it, since we had corresponded with Dr. van Nes about his work and I have a high regard for it. It is certainly true that the two papers supplement and support each other. R,E. PUTSCHER
Polarographic Studies of Some Organochlorosilanes In the article on “Polarographic Studies of Some Organochlorosilanes” [Abrahamson and Reynolds, ANAL. CHEM.,24, 1829 (1952)l the next to the last line under Procedure should read: ((treating a known concentration of hydrochloric acid dissolved E. A. ABRAHAMSON in pyridine.”
