Filtration Centrifuge Tube
tuhe. This is particularly true not only for procedures involving precious materials or radioisotopes, but also whenever the substance heing'cryatallieed is quite soluble in the recrystalliastion solvent even after cooling, so that the total volume must be minimized in order to allow good r e coveries of crystals. Normally such high solubility solvents are avoided in small scale procedures because the necessity for low volumes and limited transfer washings complicate the process. Filtration centrifuge tubes obviate these problems. The tube presented here is assembled from common laboratory equipment (no construction required), can be employed for s m d scale crystallizations and filtrations under ordinary as well as low-temperature/inert-gas conditions, and delivers mother liquor into a. vessel equivalent to the original crystallization vessel, facilitating repetition of the process. The crystallimtion is carried out in the 10 X 76 mm test tnhe A, usually seperately from the rest of t,he unit,. Inversion of this tube onto the Z m l scintered elass funnel B which is sunnorted by another 10 X 7.5 A m test tube C inside testtubes D (18 X 130 mm) snd E (25 X 150 mm), followed by centrifugation at 2000-3000 rpm, results in complete recovery of crystals a t the base or mouth of tube A and mother liquor in the bottom of tube C. Cotton F inside t,ubes D and E cushions the bases of tubes C and D, thereby avoiding localized strains which could lead to breakage in the centrifuge. The other glassglass contacts are acceptable, although the strength of each such assembly should he dry-run tested once in the centrifuge before actual use. The extra. tube E accommodstff the unit to 40-ml size centrifuge buckets. Counterbalancing only requires another tuhe E weighted with water. Use of a. rimmed test tube C allows the A-B-C unit to be withdrawn wit,h s. wireloop. An inert-gas atmosphere can he imposed by alternate evacuation and ineri-gas filling through a needle in a no-air stopper capping the entire unit. The apparatus (initially inverted relative to t,he figure) containing solution to be crystallized in A then can be cooled tolow temperature for crystallization followed by filtration. ~~
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Volume 50. Number 1, January 1973 / 81
