column, transfer 5 g of silica (Merck, Kieselgel40) in suspension in 20 mL of petroleum ether. Elute the supernatant liquid, and add the oil dissolved in 1mL of chloroform on the silica and elute with 30 mL of benzene. Evaporate the solvent under reduced pressure, and dissolve the triglycerides in 0.2 mL of chloroform. An aliquot of 20 pL is sufficient for HPLC analysis. Esterificationof fatty acids. After studying theTG by HPLC, the total fatty acid composition of the TG can be determined by GC analysis. The chloroform is evaporated and the residue is dissolved in 2 mL of methyl tert-butyl ether. Sodium methylate (1 mL) is added; the mixture is mixed well for 1 min, allowed to settle for 2 min, and then neutralized with 0.2 mL of 1N sulfuric acid. After mixing, 3 mL of water is added, and the mixture is mixed and again
allowed t o settle. The FAME contained in the organic phase analyzed by GC; inject 0.5 pL in the chromatograph.
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6. singleton, J. A ; pat&, H.W.J. Am. Oil c h h . Soc. 1984.61.161. 6. Phillios.F.C.:Erdshl. W.L.;Priveft.O.S.Lioids1984.19.880.
An Automatic Controller for a Water Still The inatallation ofan audible high-unrer alarm for the receiver ot our steam-hcnlrd water .;till has eliminated nearly a11 of the once-common flocdings due LO uverflo\r 1. The imlg cxreptims have been when absence of personnel hns left the alarm xranal unheard. The control 9ytpm has now been redesigned to hark up I he nudlhlc warning with autonintic shutc~ff of steam. Normally closed bypass valve BP can be opened if reversion to manual control is desired. Otherwise steam can reach the still only when solenoid valve SV is energized2. This occurs when START button S2 is pressed. Steam then flows until the distilled water level in the receiver has risen to approximately 1mm above the bottom edges of the electrode pair E. Cutoff can also be achieved by pressing STOPITEST button S1.
Automatic Controller. B, pulsing buzzer; D, 6.24 Zener diode: E, electrodes: F, fuse. 0.25 A: L1.6-V sensitive SPST relay: La, 1 2 4 DPDT relay; P, amber pilot lamp (POWER): p', red pilot lamp (STEAM):ps, 1 2 4 dc power supply: a, transistor MPS-A13: R,, resistor 470 K% R2,variable resistor 1 M n : Ra,resistar(see text); S,, pushbunon switch (STOPITEST):S2.pushbunon switch (START):S3. line switch. Steam system: BP, bypass valve; MV, main valve: SV, solenoid valve. The circuitry, including the 12-V dc power supply PS, is built into a Sir- X 3- X 57h-in. aluminum minibox. The momentary-contact pushbuttons, line switch, fuseholder, and pilot lamps are mounted on the front of the box. All other components, including SENSITIVITY control R2, are mounted internally. Resistor Ra allows the use of a n available 6-V sensitive relay and is not needed for a 12-V version. Momentary depression of the START button causes relay L2 t o pull in and to latch, because movement of the lower pole allows it t o supply current to the relay coil. When the electrodes are bridged by the rising level of water, Darlington transistor Q turns on, causing relay LI to pull in. This activates buzzer B and cuts off the current t o Lz, causing it to drop out. The steam supply is arrested and cannot be restarted until water has been drawn and the electrodes are no longer bridged. Thesystem, designed tocontrol steam, can obviously heapplied toother formsofheating. In essence, the critical level of any liquid that has a t least minimal electrolytic conductance can he sensed and caused to operate almost any final control element.
' Stuck. J. I'.J. C h r m Educ. 1988,62, h14. ' AscoCatalog 822 2A66, ,\utomatir Snitch Co.. $0 Hanover Hd., Flurham. SJ 079.32 John 1.Stock University of Connecticut Stows. CT 06268
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Journal of Chemical Education
