1894
ANALYTICAL CHEMISTRY
the solid and liquid phases, the time consumed and operational errors were reduced to a minimum. For general applicability, an apparatus of 60-ml. capacity is recommended. These dimensions can be altered to fit macro, semimicro, or micro techniques. The sample is weighed directly into the apparatus, a suitable solvent is added, and after shaking, the solvent is filtered off by suction. In selecting a solvent, two methods are available: (1) The solid desired is not soluble in the solvent but the other solids are; setup B is employed. (2) The solid desired is soluble in the solvent and the other solids arc not; in this case the apparatus shown in D will be very helpful and speedy. Where clogging or caking might occur, the simplest preventive technique would be to leave a few milliliters of solvent on the solid. This operation is continued until complete estraction is achieved. .hother application utilizing the same principle is shown in cy. This apparatus was designed to be used in conjunction with a centrifuge. The applicability of this apparatus may be extended to the analysis of fats, waxes, pharmaceutical preparations, and the separation of some metals. Selection of the porosity of the sinter plate is contingent on the size of particles t o be retained. Suitable filters may be selected from the five porosity grade. specified by the Ace Glass Co., Vineland, N. J.
A Multipurpose Centrifuge Cone. University, New York 58, K.Y.
r
Michael Cefola, Fordham
centrifuge is rapidly becoming a necessity in all laboratories because of the rapidity and efficiency of phase separations. With its increased use there has resulted new design in accessory equipment. This paper describes a modified centrifuge cone which can be used as a semimicro liquid-liquid or solid-liquid extractor, &s a storage container for radioactive solutions, and for centrifugations where losses due to evaporation are t o be minimized. r
HE
commodate 15-ml. cones, the cone proper should not exceed 4.5 inches in over-all length. The details which follow are related to specific uses. Microextractor. Because phases are mixed by mechanical stirring when the cone is to be used as an extractor, a Teflon bearing has been designed for the stirrer, which tapers to the same extent as the stopper. Thus, if properly machined, the st,irrer will operate smoothly, and because of the close fit of the bearing little, if any, evaporation will take place. The opening in the center has been made large enough to accommodate a dissecting needle holder which can be used as a clamp for a platinum-blade stirrer. The size of the opening in the bearing and the type of stirrer are a matter of choice. The diagram at left illustrates clearlJ-use as an extractor. Storage Container for Radioactive Solutions. Because of the graduations and the all-glass features, the cone, when used with solid glass stopper (right), will be found extremely useful in the xiorage of tracer or other radioactive solutions. I t can be easily c31eanedof contamination by the use of appropriate solvents, and used 1,epeatedly. All danger of contamination of the solutions in the (-otic!through corks or rubber stoppers, is eliminated by the u s c of a glass stopper. When working with extremely dangc.i,ouu ~naierialsit is possible to carry out all reactions in the same cone and finally make up the solution to a known volume in tlie same vessel. This minimizes the number af dangerous transfers. Becauw a1 all times the volume of solution is indicat'ed by the cone, it is possible to determine any changes in specific activity with time siiiiply by taking an aliquot of the material in question and redetermining the activity with an appropriate radiowiivity counter. Centrifugations with No Evaporation Losses. Where est raction coefficients are to be determined or losses due to evaporation at'e to be minimized, the solid glass stopper can be replaced t)y a Iiinible G l a s Co. polyt,hene cap, such as used on pharmaceutical vitils. Because of the flexibility of the st,opper material, there is no clanger of jamming.
Simple Explosionproof Light Source for Mettler Gram-atic Balances. Paul W. Mullen, Orlon Acrylic Fiber Process Control Laboratory, E. I. du Pent de Seniours & Co., Inc , Camden, 6 . C. Gram-atic balances afford a rapid, efficient, and accurate method for weighing many similar objects in routine industrial control analyses. However, two possible sources of ignition to vapors of the material being weighed or surrounding vapors make these balances unsafe for use in hazardom areas such as volatile solvent rooms, which should conform to the Kational Electrical Code for Class I occupancies. A procedure has been devised to surmount that difficulty in this laboratory and permit use of this balance in hazardous areas. On most models, a 1-inch hole on the rear of the lamp housing is provided for cooling purposes and two screw holes are punched in the top and bottom of this housing by the manufacturer Some models do not have this arrangement, but as the lamp housings arc easily detached, the necessary holes can be punched without damage to the balance. The bulb is easily removed from its mounting, revealing a focusing lens which is observed easily through the 1-inch hole. A concave mirrored reflector in an adjusting yoke, similar t o those used on microscopes, may be mounted from the top screw hole and a flashlight, Type S, approved for Class I, Group D locations, bracketed to the bottom hole. The light from this flashlight is focused on the lens by the reflector. While the scale illumination thus provided is not so intense &J that with the regular source, analysts claim the scale is easier to read because definition is sharper. The arduous and unsafe task of transporting solvent samples from a hazardous area to a weighing area ie eliminated, yet safety requirements are observed. ETTLER
1M
As the total volume of the cone is approximately 10 ml., the design calls for its use in l5-ml. shields of the International clinical centrifuge. A Pyrex brand 15-mI. graduated red line cone was cut with a glass cutting saw a t about the 11-ml. mark and to this was attached a No. 13 solid stopper joint from a 25-ml. graduated cylinder. The finished product is shown on the right of the diagram. In order to fit the head and shields which ac-
