High-Efficiency Dilution Method of Sulfuric Acid Prepared Directly in Stock Bottle with Cooler and Stirrer Osamu Nara Analytical Chemistry Department. Tohoku College of Pharmacy. 4-4-1, Komatsushima, Sendai-shl, Miyagi-ken 983, Japan
In diluting sulfuric acid for analytical use, one will typic& Iy experience hazardous heatina and fuming unless one adds su1f;ric acid t o water padualiy with manual stirring and with chilling in a container of running water. In our experience, the standard method preparation for larger quantities of the diluted solution was not always satisfactory; there is often a lack of containers large enough to hold the oversized glass vessel in which the diluted sulfuric acid solution is orenared. The necessitv of manual stirrine is troublesome and hazardous (because of splashing of t h i solution). Furthermore. it is necessarv to transfer the laree auantitv of the solution into alarge-sizk stock hottle, and ti;ei~ansfe;~rocednre is unnecessarily danperous and time consuminp. These drawhacks were notkd, a& this led to the method discribed below u,hich allows the rapid dilution of sulfuric acid directly in the glass or polyethylene stock bottles. The cooler has already been reported by Schirml, but it has not, to our knowledge, been applied to the sulfuric acid dilution procedure. This dilution method is satisfactory not only for the large quantity preparation for the use of students' experiments, but also for direct preparation in the stock bottle. Over the past few years, we have successfully applied this procedure and have achieved reasonahly safe and extremely efficient dilution of sulfuric acid with little heating and no fuming. The cooler can he used for large- and small-quantity preparations. Experimental The cooler, made of Pyrex glass, has a 25-mm 0.d. and is a 470-mm long column used in the arrangement shown in Figure 1. Preparation of 10 L of 5 N &SO, by the Proposed Method With 8 L of water in a 10-Lpalyethlenestock hottle. 1400mL of sulfuric acid was added slowly and continuously from amensuring cylinder with stining and with chilling by the cooler placed in the stoek bottle; it took approximately three minutes to finish the process of addition of all sulfuric acid. Effective cooling area of the cooler was a 220-mm-long portion extending from the bottom.
COOLING
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Figure 1. Sulfuric acid dilution assembly showing a representative in 10-L preparation of 5 NHSOI.
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Preparation of 1L of 5 N &SO4 by the Proposed Method 140 mL of sulfuric acid was added continuously into 800 mL of water in a 1-L polyethylene stock bottle, under the same procedure. Effective cooling area of the cooler was a 120-mm-long portion extending from the bottom.
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Ftgure 2 TsmperatLres at dl ffled soiffloan versus llme aner oeglnnmg addition 01 s d l ~ r i cacld 10 water Preparal on ot 10 L of 5 N H&O, oy the present method. 0 Preprat ons of t of 5 N ri,SO,.A, by the Plesenl method, and by an ordinary method with manual stirring and chilling in a bowl of running water, - - -.
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Preparation Of 1L of 5 N H2S04by the Ordinary Procedure A beaker containing 8M1 mL of water was placed deep in a. container of running water. 140 mL of sulfuric acid was added continuously to the beaker with intermittent manual stirring.
The temperature of each solution was examined after beginning addition of the acid. The temperature of the running
' Schirm, E. 2.angew. Chem. 1912, 25, 1225.
water was 20.0°C. 97% sulfuric acid (Wako Pure Chemical Industries Ltd.) was used. Magnetic stirrer (Toyo Kagaku Sangyo Co., Model DH-2) and polyethylene stirrer bar, 39 mm long, were also used. Results and Discussion There exists a need for an easier method to dilute sulfuric acid, as described. The dilution method described here has many advantages over other methods for routine dilution. Volume 63 Number 2
February 1966
155
This method. which reauires no manual stirrinp. -. chillina - in a cumbersome container of running water, and transferring the diluted solution into a stock bottle, is much safer and much more efficient than the old method. All that must he done is to add sulfuric acid gradually into the water in a stock bottle. Considerable time is saved. Figure 2 indicates that by the proposed method, sufficient cooling effect was achieved apparently from the results of 5 N HzS04 preparations. In the preparation of 10 L of 5 N H2SO4, i t took only 108 minutes to finish the process of the preparation, i.e., after beginning addition of the sulfuric acid until cooling to 25.0°C. Furthermore, with the slow hut continuous addition of sulfuric acid, the temperature of the solution rose to a maximum of 70.O0C. and though the polvethvlene bottle . . . appeared satisfactory, it onr adds the acid ar a slower mtr, or ~lrilizesa g h s bottle, this might prove more sutisfactory.
156
Journal of Chemical Education
After desired cooling is achieved, the cooler is removed, and the stirrer bar can he extracted by a magnet. The diluted solution may he stored in the container as it is, and the normalitv of the solution mav he determined as reauired. For such preparations, this dilution method provides a simple solution to the routine dilution problems, especially in large quantity preparations of volumetric solutions. This dilution method should be extremelv useful for the meparation of sulfuric acid solutions. Acknowledgment The author is greatly indebted to Ken Hara and Kyoko Ansai for their assistance and to John C. Fisher for his kindness of improving the English expressions in the manuscript. Thanks are also due to the reviewers for constructive comments.
