T H E J O U R N A L OF I N D U S T R I A L A N D Z E N G I N E E R I N G C H E M I S T R Y
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bulb and the adapter. T h e average, 0.33 cc., is equivalentzto 0.og mg. of nitrogen. TABLE I-ERROR PROM SOLUBILITY OF SOFT GLASS Acid Taken cc. 25.62 25.20 25.07 25.03 25.05
Recovered cc. 24.99 24.92 24.74 24.78 24.78
Error cc. -0.63 -0.28 -0.33 -0.25 -0.27
Using the same apparatus with I O O cc. of 50 per cent sodium hydroxide (ammonia-free) and I 50 cc. of distilled water for each distillation, t h e d a t a in Table I1 were obtained t o show the ineffectiveness of the Hopkins bulb for preventing entrained alkali from passing into the receiving acid. The error shown
Vol.
11,
No. 5
TABLE111-DISTILLATIONOF DISTILLEDWATER Acid Taken Recovered Error cc. cc. c c~. . 25.04 25.00 -0.04 25.03 25.05 +0.02 25.00 24.99 -0.01 25.00 24.98 -0.02 25.00 24.99 -0.01 DISTILLATION OF STRONG ALKALI 25.14 25.14 -0.00 25.00 24.97 -0.03 25.00 24.97 -0.03 25.00 24.97 -0.03 25.10 25.12 $0.02 ~
titration alone, 0 . 0 2 cc., which is equivalent t o 0.005 mg. of nitrogen. To show further t h a t no alkali passes through t h e scrubber, I O O cc. of ammonia-free 50 per cent sodium hydroxide and 2 5 0 cc. of distilled water were subjected t o distillation and 3 portions of 80 cc. each of distillate were collected, leaving a t the end of the distillation I I O cc. of strong alkali. The distillates were then boiled until free of carbon dioxide, cooled, and were found t o be neutral t o methyl red, less t h a n one drop of N / I O Osulfuric acid being sufficient t o impart a distinct acid reaction t o t h e solution. Three such distillations gave identical results. LABORATORY OF S O I L TECHNOLOGY OHIO~AGRICULTURAL E X P E R I M ~ STATION NT WOOSTER, OHIO
RECOVERY OF PLATINUM AND ALCOHOL FROM THE POTASH DETERMINATION By A. E. SMOLL Received December 16, 1918
FIG.2
here is the combined error of the soft glass and entrained alkali. The average, 0.78 cc., is equivalent t o 0 . 2 1 6 mg. of nitrogen. This error is too large t o be tolerated in any analytical work. Furthermore, it is not a constant error and cannot, therefore, be corrected for b y blank distillations. ‘r.4BLE 11-ERROR Acid Taken
cc.
25.05 25.05 25.30 25.07 25.00
FROM
ENTRAINED ALKALIAND SOFT GLASS Recovered cc. 24.35 24.32 24.39 24.24 24.27
Error cc. -0.70 -0.73 -0.91 -0.83 -0.73
The Hopkins bulb and the adapter were then replaced by the new devices and distillations again made as above. The results are found in Table I11 and they show t h a t the errors from the soft glass and entrained alkali have been eliminated b y the employment of the scrubber and adapter made of Pyrex glass. T h e error is approximately the same as t h a t found for
There:have been worked out several methods for the recovery of platinum used in the potash determination, but never has there been one, a t least t o t h e author’s observation, for t h e recovery of the alcohol. At t h e current price of alcohol, where grain alcohol is used in the determination, i t proves t o be quite a n item where large numbers of t h e potash estimations are made. I t is true, however, t h a t in some instances part of t h e alcohol has been redistilled, but i t was found t h a t the slight amount of acetaldehyde present had the tendency t o lower the p o t y h results on t h e subsequent determinations. With this thought in mind, the author has worked out a method whereby the platinum is reduced t o platinum black a s by t h e zinc a n d hydrochloric acid method, and with a little additional attention the alcohol is also recovered. The alcoholic washings are saved in the usual manner until a few liters have accumulated, 5 liters or more being advisable. A 2-liter distilling flask is connected with a condenser, preferably a coil condenser, and t h e alcoholic washings are transferred t o the flask and distilled with t h e usual precautions. The electric hot plate is the most reliable source of heat and will eliminate the fire risk. A small metal disk which will accommodate the bottom of the flask is partly filled with sand and the flask allowed t o stand in this. If a hot plate with three heats is used i t can be so regulated as t o meet the demand of the operator. Small pieces of glass rod 1 / 4 inch in length rounded over a t each end will prevent bumping and can be easily washed free of any adhering platinum black which is reduced upon boiling of the solution.
May, 1919
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
The distillation is carried on until the boiling point of the distillate is 100’; this will insure all the alcohol being removed. The flask is then emptied of what remains, including the bulk of the platinum black t h a t has been reduced. Then the flask is refilled and the operation repeated until all the washings have been treated. A t the end the flask is washed free of all the platinum black. A t this point the platinum has all been reduced and can be washed and treated further in its recovery as in the method where zinc and hydrochloric acid are employed. The next procedure is the removing of the aldehyde from the alcohol, which is easily accomplished by means of fractional distillation. The flask is set up as in the first operation except t h a t this time i t is connected directly with a n Allihn condenser, serving the purpose of a reflux condenser. As the aldehyde boils a t about 2 I O and the alcohol a t 7 8 O , their separation is easily effected. Warm water should run through the Allihn condenser and should be so regulated t h a t This is hot a t the outlet the temperature is 58’. enough t o allow the aldehyde t o escape and a t the same time condense the alcohol provided the boiling is not too vigorous. At the top of the Allihn condenser is a delivery tube t h a t leads t o the coil condenser used in the first operation. This can be used t o condense the aldehyde and what small amount of alcohol is liberated. The distillation is carried on until the distillate from the coil condenser shows no trace of aldehyde. A simple and delicate test is made by mixing a few crystals of phenol with 5 cc. of concentrated sulfuric acid in a test tube. Three cubic centimeters of the distillate from the outlet of the condenser are caught in a test tube, one cubic centimeter of the acid mixture added and the whole shaken. If there is a trace of aldehyde a reddish brown solution will result; if not, a colorless solution will persist. The operation is continued until the alcohol is freed of all the aldehyde. Then the alcohol is removed, the flask refilled with the alcohol containing the aldehyde, and the operation repeated until all the alcohol has been freed from the aldehyde. When the distilling is completed, if the volume of the distillate of t h e aldehyde mixture is sufficient, i t can be re-distilled t o recover alcohol liberated with the aldehyde. Then a few pieces of sodium hydroxide are added t o the distilling flask which can be connected directly with the coil condenser and the alcohol is distilled until the sp. gr. 0.8645 is obtained. This is the specific gravity of the alcohol used in the washing of the potassium chloroplatinate as given by the official methods. The first impression may be t h a t the operation is lengthy and requires considerable attention, but in actual use i t is quite the opposite. I n fact, it can be handled along with the regular laboratory work and inconvenience one very little. Last year the author recovered 40 liters of alcohol in this manner in connection with the platinum recovery and the process required only little attention. Where a large number of potash determinations have t o be made, necessi-
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tating in the course of time the consumption of large quantities of alcohol, i t is well worth considerable effort t o recover the alcohol. CHEMICAL LABORATORY DOLDPACKING COMPANY
JACOB
WVICHITA, K A N S A 5
A SlMPLIFIED SIGNAL DEVICE FOR THERMOMETRIC READINGS-COAL CALORIMETERS B y H. s. V A S 5 A R Received February 20, 1919
I n a recent number of THISJ O U R N A L ’ appeared a description by Chas. A. Myers, Jr., of a timing device used in the chemical laboratory of the New York Navy Yard for giving “warning” and “reading” signals when making calorimeter determinations.
FIG. I
I n applying this equipment to a smaller laboratory where but two calorimeters are in operation certain changes have been made simplifying the equipment and giving very satisfactory results. The apparatus used (Fig. I ) consists of one zo-ohm relay, one single stroke bell, 3 dry cells, and the same “timer” 20 O b as t h a t used by Mr. I Relay Myers, connected as shown in the accompanying sketch. Aside from the simple wiring the only labor required Flexible Leads was t h a t of placing the contacts on the clock and wiring them t o the 3 binding posts on the clock case. Instead of cementing platinum foil contacts t o the clock face, con1/2 minute switch tact pieces cut from German silver are fastCut Off switch ened in place with small machine screws FIQ.2-TIME SIGNAL DEVICEFOR C O A L CALORI~SETER and nuts. I n installing this equipment the switches for starting and for cutting the half-minute signal “in” or “out” were mounted on the edge of the calorimeter table convenient t o the operator; the relay, bell, and
/I
1 1 0 (1918), 101.5.
