ANALYTICAL CHEMISTRY
922
pre-asher a t an appropriate distance from the reflected heat. The sample will be completely charred in from 15 to 60 minutes, depending on the amount of sample taken. If sulfated ash is desired,. add 5 ml. of diluted sulfuric acid to the sample before charring. Once the sample has charred, place it in the muffle furnace for complete ashing a t a temperature of 500’ to 550’ C. When white ash is obtained, cover the dishes and place them in a desiccator until cool enough to be weighed. Liquids. For liquids such as soft drinks, beer, milk, etc., measure 50 to 100 ml. of the sample, pour it into a tared 100-ml. dish, and place it in the pre-asher. Carbonated liquids should first be decarbonated (1). After the sample is charred, continue as above. 4 number of replicate ash determinations were made using the pre-ashing procedure, and the results were compared with values obtained using the procedures of the Association of Official ilgricultural Chemists and the American Society of Brewing Chemists. On such diverse materials as molasses, malt sirup, corn sirup, beer, cola beverage, salad dressing, jam, and lupulin the pre-ashing procedures gave comparative results with substantial saving of time. ACKNOWLEDGMENT
The author wishes to express his thanks to W. A. Beck of Ekco Products for his contribution in fabricating the apparatus, to T. J. Stewart of Wahl-Henius Institute for furnishing samples used in testing the pre-asher, and to the American Institute of Baking Laboratory staff for their cooperation and advice. LITERATURE CITED
(1) Am. SOC.Brewing Chemists, “Methods of Analysis of the
American Society of Brewing Chemists,” 6th ed., p. 11, 1949. (2) Ibid., p. 32. (3) Assoc. Offic. Agr.
Chemists, “Official and Tentative Methods of Analysis,” 6th ed., p. 559, 1945.
bath when a large piece of work placed in the plating bath raises the bath level. This makes them practically useless for plating baths. Of the levelers described, that of Telang seems the most satisfactory, but it requires a tightly stoppered reservoir. The electrical devices are not convenient for use with small baths and are rather expensive. The construction of a new type of leveler is shown in Figure 1. The water enters from the tap through tube A and flows out through tube B. When the bath level drops, float F lowers, and the water flows through tube D over the edge of cup E and down the stem of the float into the bath. .4s the bath level rises, D is closed by the mercury pool, E , and all the water is rejected through B. The depth of mercury in E need be only a few millimeters in order to hold the 2- to 3-cm. head of water above it. These levelers can be made in any size, for solution depths of 10 cm. or more. They will maintain the level constant to within 5 mm. None of the dimensions is critical. However, D should be of sufficient size so that it will not become clogged by the small particles of sediment that may enter with the taD yater. -4 5-mm. tube is a convenien’t size. The mercury pool cup must be large enough and so centered that it will slide freely up over D without touching. The overflow tube, B, should be about 2 cm. in diameter, in order that the water will flow out freely. A small air vent a t C prevents the column from flooding with water. F should have about a 3-mm. clearance between it and the surrounding tube. By removing the small pin a t the bottom of the leveler tube F can be removed. The leveler may be constructed of materials other than glass, or glass levelers may be placed inside stainless steel tubes to prevent breakage.
r
Constant-Level Device for Liquids. Dwight E. Couch and Abner Brenner, National Bureau of Standards, Washington, D. C. for maintaining a constant level of liquid in tanks are D commercially available. Most of these employ an electrical EVICES
circuit to operate a solenoidal valve or pump, but there are no satisfactory devices for use with small installations such as electroplating baths operated a t elevated temperatures.
In 1909 Fitzgerald ( 1 ) described the familiar inverted bottle type of leveler for use with hot baths or filters. A better system which uses a siphon and a tightly stoppered bottle arrangement has been described by Noga (7). In 1924 a siphon type of leveler, which uses the water directly from the tap and supplies it to the bath, was described by IVilde (14). This article inspired Jefferson ( 3 ) to describe a simpler setup which he had employed in 1905. On this leveler he had attached a reservoir to prevent the accumulation of a small amount of air from stopping the siphon. In 1925 Stehle (IO, 11), modified Jefferson’s setup by replacing the bubble-catching reservoir a i t h a secondary siphon to prevent the entrapment of air in the siphon tube. Snell(9) and Sissan (6) described a siphon leveler similar to Wilde’s. Pocock (8)used an arrangement very similar to the one used by Noga. Telang (12) applied a useful modification to these levelers which eliminated the possibility of the siphon’s failing through air entrapment. An electronic circuit was used by Hersh et al. ( 2 ) . A patent was issued to Le Fever (6) in 1931 on an electrical circuit which regulated the water level in a sump between t n o predetermined levels. Minor variations of this circuit were later patented by \Varrick (13). Another device, using a floating ball which contains some radium to actuate an electronic circuit, has been patented (16). An adaptation of Le Fever’s circuit to an electroplating bath was described by Kushner ( 4 ) ,who used a solenoidal valve for the water control and equipped the leveler with a warning bell as a safety device. These devices have certain shortcomings. Siphon levelers that receive water directly from the tap will siphon off part of the
Figure 1. Schematic Diagram of Level Regulator A . Water i n l e t from
This neiy leveler eliminates many of the disadvantages of other types. I t takes water directly from the tap. It is of simple construction and is compact and easy to move from one bath to another. One leveler has been used on a 6-liter bath operating a t 85’ C. and another has been used on a chromium plating bath of commercial size (3000 liters). Both have operated satisfactorily for several months. Although originally designed for laboratory use, the leveler may be used on large installations.
tap
B . Water
o u t l e t to drain C. Air i n l e t D. Water flow t u b e to bath E. Cup a n d mercury valve F. Float G. Approximate water level
ACKNOWLEDGMENT
The authors wish to acknowledge suggestions of Seymour Senderoff and Charles Bauer which have been incorporated in the design. LITERATURE CITED
(1) (2)
Fitzgerald, IT. P., J . Am. Chem. Soc., 31, 839 (1909). Hersh, R. E., Fry, E. >I., and Fenske, >I. R., I n d . Ettg. Chem., 30, 363 (1935).
(3) Jefferson, R. E , Ibid., 16, 1230 (1924). (4) Kushner, J. B., Metal Finishing,43, 102-6 (1945). (5) Le Fever, H. hI., U. S. Patent 1,820,981 (1931). . 20, 592 (1948). (6) Sissan, A. H., h . 4 ~ CHEM., (7) Noga, E., Chem.-Ztg., 35, 977 (1911). (8) (9) (10) (11)
(12) (13) (14) (15)
Pocock, B. W., IND.ENG.CHEM.,ASAL.ED.,14, 811-12 (1942). Snell, C. A , , and Snell, F. D., d s a ~CHEM., . 20, 186 (1948). Stehle, R. L., I n d . Eng. Chem., 17, 486 (1925). Stehle, R. L., Science, 6 3 , 404 (1926). Telang, M.S., IND.ENG.CHEM.,ANAL.ED.,18, 453-4 (1946). Warrick, C. F., U. S. Patent 2,249,994 (1941). Wilde, H. D., I n d . Eng. Chem., 16, 904 (1924). Wolf, A,, U. 8. Patent 2,456,233 (1948).
