A Flask for Separation of Serum from Blood FREDERIC E. HOLMES AND BARBARA JOHNSON Children's Hospital Research Foundation and Department of Pediatrics, College of Medicine, University of Cincinnati, Cincinnati; Ohio
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fusing, in a hole of slightly smaller diameter than the rod in the end of a wooden dowel which is split to a distance of about 50 mm. from the end (C). The bottom of the flask is heated strongly at the point where the rod touches it. While thiE region of the glass is soft, the rod is lifted about 5 mm. to form an inwardly directed cone at the base of the rod t o decrease the internal stresses in the glass. The glass is then allowed to cool slightly, so that the wooden dowel can be pulled away from the rod. During the entire process, the.lower half of the flask must be kept hot by frequent heating in a bushy flame, and at the end, the finished vessel must be placed immediately in an annealing oven at between 550" and 570" C. If it is not annealed, the vessel will inevitably crack, but it remains strong indefinitely if well annealed. The outlet tube is of 7-mm. (outside diameter) glass tubing. The rods used for pegs are of about 6-mm. diameter, and are between 35 and 40 mm. long near the outlet and between 50 and 60 mm. long at the opposite side. The pattern of placement of the pegs ( B ) promotes contraction of the clot toward the center and provides a weir to prevent blocking of the outlet by the sagging clot.
HE centrifugation of relatively large ainounts of whole
blood in the ordinary equipment involves time-consuming operations. I n freeing the clot from the sides of the centrifuge bottles in order to obtain a better separation of serum from the clot, considerable hemolysis may unavoidably be produced. The simpler method of allowing the blood to clot, undisturbed, in a plain vessel, is much used in obtaining serum free of red blood cells and products of hemolysis.
The design of the 1-liter flask described can, of course, be used in both smaller and larger vessels, and the use of pegs may be applicable in vessels of sufficient size for commercial use. Flasks of the type described should be especially useful for the recovery of maximum yields from unavoidably limited sources-for example, for the separation of convalescent serum for immunization.
c. A. FIGURE 1. FLASKFOR SEPARATION OF SERUM FROM BLOOD A . Normal view B. Plan view of bottom, showing airangement of glass pe 8 and their relation t o outlet tube C. Woo&n dowel, partiy in section, with glaas rod in place ready for fiision to b o t t o m of flask
An Ether-Insoluble Stopcock Lubricant B. L. HERRINGTON, Cornel1 University, Ithaca, N. Y. AND
The contracting clot retains the red cells and extrudes clean serum. However, it is difficult to recover the last portion of the serum, either b y drawing i t off through a tube or by pouring it off from the clot, without bruising the clot and liberating small amounts of cells or hemoglobin. I n the vessel shown in Figure 1, this difficulty is overcome and the yield is increased by the simple expedient of placing a number of pegs in the bottom of the flask. The clot forms and contracts on the pegs, which hold i t without bruising while the serum drains off completely through the outlet tube. The flask has been used routinely in this laboratory for several years for the recovery of goat serum.
illORTIhlER P. STARR, Brooklyn College, Brooklyn, K,Y.
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THE conventional type of stopcock grease was found un-
satisfactory for the lubrication of separatory funnels in which lipids were extracted from an aqueous suspension with ethyl and petroleum ethers. The greases were sufficiently soluble in the ethers to cause, in certain cases, a significant increase in the weight of the extract. Omission of the lubricant was impractical because of leakage, and because the ungreased stopcock would stick and not allow the precise adjustment needed for the exact separation of the two layers. I n order to overcome these difficulties, a starch-glycerol gel was tried as lubricant and found very satisfactory. Although it is slowly soluble in water, one application proved sufficient for fifteen successive extractions. It is not dissolved b y the ether layer; no increase in weight of extract could be detected even when some of the lubricant was placed directly in the funnel. This particular gel was prepared by suspending 9 grams of soluble starch in 22 grams of glycerol and heating to 140" C. After standing a short time, the clear solution was decanted from the sediment in the bottom and allowed to cool. The next morning, this mixture had the consistency of a heavy grease. It has proved very satisfactory for the authors' purpose, and may prove useful to others who need a lubricant which will not dissolve in nonpolar compounds.
Durin filling, the flask is tipped away from the outlet tube, and the %lood is delivered through a clean gum-rubber tube to the bottom of the flask until the pegs are covered and the edge of the pool of blood reaches to just below the outlet tube. The vessel is held in this position on a suitable support until a firm clot has formed and some of the serum has begun to separate from it. The flask is then tipped back t o or slightly beyond the upright position and held thus until the serum has all been extruded and has drained through the outlet tube into a receiving vessel. An assembly of apparatus including a needle, the flask, a receiver for the serum, and connecting rubber tubing, can be sterilized as a unit and used t o obtain sterile serum from blood taken directly from the vein of the animal. For this purpose only standard devices and familiar bacteriological technique are required. In making the vessel, the outlet tube is first fused onto the side of a 1-liter Erlenmeyer flask near the bottom, and then the glass rods are fused in place. The rods are conveniently held, during
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