Stabilized blood separating composition

Claim 1

In a method of separating a sample of whole blood into serum and clot portions which method comprises centrifuging a sample of whole blood in the presence of a thixotropic water-insoluble composition having a specific gravity in the range of about 1.030 to about 1.090 and consisting of silicone fluid and a siliceous filler dispersed therein, the improvement which comprises using such a composition with a network former added thereto, the network former consisting of a polysiloxane-polyoxyalkyl copolymer in a quantity sufficient to maintain the viscosity of the composition within the range of about 200,000 to 600,000 centistokes for prolonged periods of time; wherein the polysiloxane-polyoxyalkyl network former is a copolymer represented by the formula ##STR2## where the monomeric units are randomly distributed and Me represents --CH 3 ; x represents a number between 80 and 120; y represents a number between 8 and 12; P represents a polyoxyalkyl side chain represented by the formula CH.sub.2 --CH.sub.2 --O).sub.m (CH.sub.2 --CH.sub.2 --CH.sub.2 --O).sub.n where the monomeric units are randomly distributed and m represents a number between 20 and 30; and n represents a number between 1 and 30.