AIDS FOR THE ANALYST pilot light is installed in parallel with the heating initial temperature adjustment.
Automatic Apparatus for Fluoride Distillation Wesley B. Estill' and Loren C. Mosier, Ozark-Mahoning
i
d
to fitcilitatc
Co.,Tulso, Okla.
~ I N C Ethe
advent of the Willard and Winter distillation proLcedure (6) for separating fluoride from numerous interfering substances prior to analysis, considerable effort has been put forth to decrease t h e time necesqary for distillation ( 2 , 4) and/or make the distillation operation more automatic ( 1 , 3, 5 ) . Both improvements would in the end save man-hours, and give more reproducible results.
Although there may be some bumping in the liquid a t the outset, this ceases when steam is introduced and no perrhloric acid has been carried over to interfere in the subsequent determination of fluoride, as occasionally occurred before adoption of this unit, when distillation temperatures were allowed to go too high. T h e small side tube through which the vapors pass to the condenser is made to protrude about 2 mm. through the nall of the larger side arm. This feature of construction, the f w t that the liquid level is kept low in the distilling flask, and the close temperature control effected b y the thermostat have appeared t o eliminate distillation difficulties completel). (Tahle I). T h e effects of the presence of other compounds \\-ere assumed to he the same as in other type3 of fluoride distillation equipment. T h e rate of steam generation is not critical, if the distillatiori flask is not cooled below its operating temperatiirc. LITERATURE CITED
4lIlU
\ \\
Churchill. H. V., ISD. Eso. CHEM.,A s a L . En., 17, 7 2 0 (1945). (2) Frasier, It. E , , and Oldfield, H. G., Public Heaith Rep!s., 68, 729
'
(1)
(1953. (3) Hackahoy, !I7, B., Welch, E. T., and AIetler. 1.\.., .Is.\L.CHEM., 19, 154 (1947). (4) Richter. F.. Z . anal. Chem.. 124. 161-216 (194%). (5j Tillard, H. H.. and ITinter, 0. B., ISD.E&. CHEY.,.\SAI,. EI)., 5, 7 (1933). ( 6 ) Willard, H. H., Torihara, T. Y., and Holland, L. X., .L~-.\I..C H E X . , 19, 343 (1947).
$7
U
110 V O l I ,
S T E A M GENERATOR
DISTILLATION F L A S K
WDENSER
a
PRESENTED beiore the Tri-Secttonal XIeeting, Rartlesl-ille, Okla., October 17. 1953.
RECEIVEB
.iSlERIC.As C I I t X I C I I I
Sou!tTY,
Figure 1
Digester and Filter for Preparing Extract Solutions from Solids
Probably the greatest obstacles t o general use of automatic control for fluoride distillation have been t h e high cost of fabricating a satisfactory unit and the addition t o the basic apparatus of a large amount of extra equipment TThich makes the operation of cleaning equipment and changing acid somewhat laborious. T h e automatic unit designed b y t h e authors is shown in Figure 1.
George R. Van Atta and Jock Guggolz, Western Utilization Research Branch, Agricultural Research Service, U. S. Department of Agriculture, Albany 10, Calif.
figure depicts a type of apparatus found Tusefulaccompanying for digesting or ext,racting solids such as plant materials HE
which require repeated lixiviations with fresh port,ions of solvent or reagent solution. I t s use avoids t,he bothersome t,rarisfcr of the entire digePtion mixture to a separate filter for withdrawal of each successive extract solution and subsequent return of the, drained solids to a digestion vessel for the next extraction. As either lixiviat,ion or digestion is accomplished in a single vessel, hot extract solutions can be drained from residual solids x i t h but little cooling. Liquid losses by vaporization during digestion or extraction can be prevented hy use of a reflux condonser. This apparatus is similar in principle to the vomnionly used microheaker filter descrihed by von Bergkampf [Bergkampf, 1 Present address, Oak Ridge, Tenn. E. S. von, Z. anal. Chem., 69,32141 (192611. T h e presrnt design, however, was developed for work Table I. Titration of Fluoride primarily with macro samples. Direct Titration without Distillation Titration after Distillation in Proposed Still T o this end a spherical flask is F, Factor, F, Factor, employed and contributes tht: mg. F-/ml. Deviation mg., TitraTitramg., mp. F-/ml. Deviation tion std. Th(IiO8)r from mean tion std. Th(XOa)i from mean ruggedness needed in a larger unit. Furthermore, absence of 2.55 1.962 -0.032 2.50 5 2,000 ' 0 010 2.52 -0.007 1.987 2.53 5 1.978 -0 012 square corners where solids could 2.50 2.000 2.54 +0.006 -0.020 5 1.970 2.50 2.000 2 52 +0.006 5 1.985 -0.005 tend to lodge facilitates admix2.53 -0.016 1.978 2.49 5 2.008 4-0 018 ture of thecharge and recovery of 2.53 1.978 -0.016 2.53 -0.012 5 1.978 3.03 1.982 -0.012 3.00 +0.010 6 2,000 undissolved residual solids. I n 3.00 2.000 +0.006 2.99 6 2.008 +o 018 2.96 2.028 +0.034 3.02 6 1.987 -0.003 the authors' experience use of 3.00 2.000 +0.006 Mean 1,990 &0.0120 2.99 standard-taper glass joints and 2.015 +0.021 3.01 6 1.995 +o 001 the accessories sho\vn are also deMean 1.994 f0.0136 sirable feature? of the present design.
T h e glass-enclosed thermostat (Fenwal KO. 17000 is recommended), which can be adjusted to a predetermined value, is connected in series Kith the heating coil. At 135" C. this thermostat is capable of controlling t h e temperature within f 1 ° C. .4s soon as the desired distillation temperature is reached, t h e steam valve is opened t o allow the steam t o enter the perchloric acid. Aside from t h e fact t h a t i t is necessary t o open the steam valve manually the distillation is completely automatic. T h e distillation flask is custom-made for t h e unit. T h e heating coil was fabricated b y t h e authors to draw about 100 watts. T h e
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