Drying agents, soluble

Calcined Anhydrite. Soluble anhydrite, or second-settle stucco, has physical properties similar to those of gypsum plaster. It hydrates to the dihydrate rapidly in water. Its outstanding property is its extreme affinity for any moisture, which makes it a very efficient drying agent (see Desiccants). In ambient moisture-laden air, it readily hydrates to hemihydrate. Soluble anhydrite, under the trade name Drierite, is widely used as a desiccant in the laboratory and in iadustry. A small amount is also used as an insecticide carrier. Small amounts of soluble anhydrite are unintentionally produced in most commercial calciners during hemihydrate production. 

C. (E)- -Iodo-4 -phenyl-2-butene. In a 20-ml., round-bottomed flask are placed 2.0 g. (0.008 mole) of 2-(4/-phenyl-l -buten-3 -yl)thio-2-thiazoline, 5 ml. of methyl iodide [Methane, iodo-], and 2 ml. of di-methylformamidc. The resulting solution is heated at 75-80° for 2.5 hours under a nitrogen atmosphere (Note 13), cooled, and poured into 10 ml. of water. Extraction with three 12-ml. portions of ether separates the product from water-soluble by-products. The extracts are combined, washed with 8 ml. of 1% aqueous sodium thiosulfate and two 8-ml. portions of water, dried over anhydrous magnesium sulfate, and filtered to remove the drying agent. Removal of ether by distillation at 30° (100 mm.) leaves 1.5-1.7g. (74-82%) of ( )-l-iodo-4-phenyl-2-butene (Notes 14 and 15). 

Fisher Scientific Company (reagent-grade) or Matheson Coleman and Bell. The first two were slightly yellow, and the latter was colorless however, the yields of final product were identical with each brand. The excess thionyl chloride serves as a drying agent for the hexanoic acid and as a solvent for the IV-bromosuecinimide, which is not very soluble in carbon tetrachloride. 

Ointments are semisolid preparations that are intended for external use. Ointments may contain either finely powdered drugs or their mixtures, liquids, and other drug forms incorporated into appropriate bases. They are applied to the skin for their physical effects as emollients (which make the skin more pliable), protectants, lubricants, and drying agents. Ointment bases are also used as vehicles in which to incorporate topical medications which exert specific effect. There are four types of ointment bases, namely, oleaginous, absorption, water removable, and water soluble bases. 

Uses. The insoluble anhydrite is used in cement formulations and as a paper filler the soluble anhydrite is used as a drying agent the hemihydrate is used for wall plaster and wall-board gypsum is used in manufacture of plaster of paris and portland cement. 

Coball(lI) hydroxide exists in two allolropic forms, a blue or-Co (OH) and a pink /l-Co(OH) . The hydroxide is prepared by precipitation from u cobaltous salt solution by an alkali hydroxide. When the alkali is in excess the pink ft form is produced—the blue a-furni is produced when the cobalt salt is in excess. The salt slowly oxidizes in air at mom temperature and changes to hydrated cobaltic oxide, Co-Oi - H 0. The hydroxide is practically insoluble in H 0 and in bases, but highly soluble in mineral and organic acids. The commercial salt is used as Ihe starting material in the preparation of drying agents. 

Specialty Isocyanates. Specialty isocyanates are organic isocyanates having the isocyanate function attached to a carbonyl group or to elements other than carbon. /t-Toluenesulfonyl isocyanate is used as a drying agent for organic solvents. Arenesulfonyl diisocyanates, such as m-phenylenedisulfonyl diisocyanate, are used as monomers for base-soluble polymers. Arenesulfonyl monoisocyanates are used as intermediates for pharmaceuticals and herbicides. 

This solvent is fairly pure as received. The only impurities are water and traces of dimethyl sulfide. Dimethyl sulfide can be removed by a preliminary vacuum distillation, or by bubbling an inert gas through the solution for 10 to 20 min before use. The water content can be reduced to 10 ppm by sequential treatment with two batches of 3 A molecular sieves (activation of the sieve at 500°C for 16 h in an inert atmosphere has been advocated [62], but activation for 15 h at 300°C should suffice [52]). Calcium hydride and a number of other basic reagents have been advocated as drying agents, but in fact all of these are ineffective [32]. Tetrabutylammonium hexafluorophosphate exhibits good solubility in THF. 

A small portion of the product is tested for any unreacted platinum(IV) chloride by leaching with a few drops of hot water. An equal volume of a saturated solution of ammonium chloride is added to the leach water, and if there is no precipitate within 1 minute the product is pure. If a precipitate appears, the entire product should be leached with water until free of the soluble platinum(IY) chloride. The purified product is partially dried by suction filtration and finally completely dried by a drying agent in a desiccator. The yield is 2.8 g. (91% based on H2PtCl6-6H20). Anal. Calcd. for PtCl2 Pt, 73.3 Cl, 26.6. Found Pt, 73.0 Cl, 26.8. ... 

---