Vol. 3, No. 3
ANALYTICAL EDITION
320
sufficient, Some assurance is given to this assumption by actual steam-condensate readings from Stirling boilers in the mho, with no correction for carbon diorder of 0.5 X oxide. The previously suggested correction of 0.9 X 10-8 mho is therefore believed to be too high. Having made the above corrections and obtained a value for solids in the steam under different operating conditions, one may arrive at some conclusions as to the best practical method of operation to give the lowest solids and theoretically the least amount of trouble from deposits. However, the total amount of solids found is not an infallible guide to the quantity or rate of deposit formation and the type of equipment and the use to which the steam is put must be considered. Previous experience and results will also be of material aid in reaching reasonable conclusions. The analysis of the boiler water is often a guide to the probability of deposit formation, and after some experience with a .certain system, it is possible to set certain limits of boiler-water concentrations below which trouble may be avoided. For example, limits placed on the silica or other solids in the boiler water have been found to be effective. In addition to the above, the conductivity method is often useful in comparing the solids in the steam from different boilers or other apparatus, such as evaporators, and trace the source of the largest amounts of solids. For certain practical purposes, it is not always necessary to go through the entire procedure as far as the calculation of solids. That is, the results in terms of specific conductivity of the steam condensate will indicate whether a large
An Extractor for Biological Products‘ Chas. L. Shrewsbury
or small amount of solids is present, particularly when the carbon dioxide has been largely removed by use of the gas separator and condenser. However, to develop the art and obtain records which will be useful for a complete study of deposit formation, the general practice should be to obtain complete information. It is concluded that despite some evident sources of error in the methods which must be used in practical work, the conductivity method of estimating solids or equivalent moisture in steam condensate will be a valuable aid in the study of power-plant and related problems. Similar electrical conductivity methods of estimating condenser leakage and boiler water solids have enjoyed considerable popularity and success. Acknowledgment
Acknowledgment is made to the personnel of the Research Development Department of the Babcock & Wilcox Company and others for helpful suggestions in developing the method. Literature Cited (1) Commonwealth Edison Co., N . E . L. A . Publication, No. 051, 14-9 (June, 1930). (2) Creighton and Fink, “Electro-Chemistry,” Vol. I, pp. 89-91, 2nd ed., Wiley. (3) Fitze, Power, 68, 484-5 (1928). (4) Hecht and McKinney, “Electrical-Conductance Measurements of Water and Steam,” paper presented before Am. Soc. Mech. Eng., June, 1930. (6) Washburn, J . Am. Chem. Soc., 40, 89-91 (1918).
means of the siphon tube, e. The operation of the extractor is continuous and automatic. The extractor has a capacity of approximately 5 liters and will hold from 3 to 5 kg. of feeding stuffs.
PURDWE UNIVERSITY AGRICULTURAL EXPERIMENT STATION, LAFAYETTB, IND.
HE extraction of large amounts of materials for use in nutrition investigations becomes a problem with the apparatus that can be fabricated or purchased. Guerrant (I) described an extractor that can be assembled in most laboratories. Experience has demonstrated that considerable quantities of vapor escape through the seal between the bell jar and desiccator top in this type of extractor. I n addition, one must use a liberal application of sealing compound a t this joint which may contaminate the solvent and which is objectional when the extract is to be incorporated in feeds. The extractor illustrated in the photograph is one that was designed with the view of eliminating the above objections. The extraction chamber, a, is molded of medium-weight glass that will withstand rapid temperature changes and moderate negative pressure. It is fitted with a ground glass top, b, which is provided with a ground glass opening to receive a condenser, c. The condenser is constructed so that vapors are led directly into the extraction chamber, providing for a hot extraction of the material. If the cold extraction process is used, the vapors are led in through the top of the condenser. The ground glass condenser and top joints require little or no sealing compound to effect a tight seal. When operating without sealing compound, no difficulty has been experienced with the top becoming fast or with loss of solvent. The solvent is placed in a 6-liter round-bottom Pyrex flask, d, and heated on the steam bath. The condensed vapors and extractives are returned to the boiling flask by ‘Received March 12, 1931.
An Extractor for Biological Products
Literature Cited
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(1) Guerrant, N. B., IND. ENG. CREM.,18, 1090 (1928).
