Compact crystals

To two liters of a culture so prepared there is added under sterile conditions a solution of 500 mg of 17a-methyl-testosterone in 15 cc of acetone. Shaking is carried out for 3 days at 27°C, the mycellium then filtered off with suction, washed with water and ethyl acetate and the combined filtrates extracted with ethyl acetate. The extraction residue obtained after evaporation of the solvent is dissolved in a little acetone. On addition of ether, the 1-dehydro-17a-methyl-testosterone is obtained in compact crystals. MP 163° to 164°C. 

Solutions of biphenyl-2,2 -diamine (7.4 g, 40.2 mmol) in hot HOAc (40 mL) and phenanthrene-9,10-dione (8.3 g, 40 mmol) in HOAc (160 mL) were mixed and kept at 100°C for 2 h. After 12 h cooling, a canary yellow, crystalline powder was filtered off yield 11 g (77%). Recrystallization from excess boiling HOAc gave small, compact crystals mp 268-269 C. 

The concept zeolites conventionally served as the synonym for aluminosilicates with microporous host lattice structures. Upon removal of the guest water, zeolites demonstrate adsorptive property at the molecular level as a result they are also referred to as molecular sieves. Crystalline zeosils, AlPO s, SAPO s, MAPO s (M=metal), expanded clay minerals and Werner compounds are also able to adsorb molecules vitally on reproval of any of the guest species they occlude and play an Important role in fields such as separation and catalysis (ref. 1). Inclusion compounds are another kind of crystalline materials with open framework structures. The guest molecules in an inclusion compound are believed to be indispensable to sustaining the framework structure their removal from the host lattice usually results in collapse of the host into a more compact crystal structure or even into an amorphous structure. 

Phenyl methyl selenium bromo-iodide, (C6H5)(CH3)SeIBr, is obtained when the dibromide is triturated with a cold solution of potassium iodide of the same concentration. The yield is quantitative, and the product separates from alcohol as red, ill-defined, compact crystals, M.pt. 85° C. with decomposition. Heating at 100° C. causes quantitative decomposition to methyl iodide and bromoselenobenzene, the reaction being represented as follows r... 

When the benzene mother-liquors from the compound described above are evaporated under 20 mm. pressure, a black viscous tar remains. This is extracted with chloroform and the extract added to the original chloroform extract of the crude condensation product. Concentration of the mixture yields a pink crystalline material three recrystallisations from chloroform giving colourless compact crystals, decomposing at 213° to 214° C. The complex is slightly more soluble in hot chloroform than in the cold solvent, and dissolves readily in alcohol or acetone. 

Suitable material is available from Pfanstiehl Laboratories, Waukegan, Illinois. It may also be prepared from the hydrochloride of 2-amino-2-deoxy-D-glucose (D-glucosamine) in 95% yield by the facile procedure of Inouye and co-workers.2 The 2-acetamido-2-deoxy-D-glucose should be dried at 25° (1 mm.) for at least 12 hours before use. If this material is in the form of a powder rather than compact crystals, more acetyl chloride... 

Pb4SeBr4 5 g. PbSe 9 Af HBr 65 350 335 5 Nearly black compact crystals, much... 

In its compact crystal structure, the two opioid tetrapeptide pharmacophores of biphalin are not conformationally equivalent. One tetrapeptide, which has a steric similarity with the delta-selective peptide DADLE, folds into a random coil. The contralateral tetrapeptide, sterically similar to the mu-selective peptide D-TIPP-NH2, exhibits a fairly normal type III (3 bend [4]- These conformational features suggest that under physiological conditions, biphalin may easily bind to these respective opioid receptors. This duality of binding affinity is probably the reason that biphalin is able to interact with all opioid receptor types. 

Using symmetric, compact crystals gives more predictable and consistent performance Desirable particle size range can be obtained such crystals exhibit good flowability and less sedimentation in suspensions... 

Rapid or shock cooling and high agitation favor the formation of thin, small crystals and should be avoided. Slow crystallization by evaporation yields compact crystals. 

When a powder resides in a storage container for a period of time without moving, it can become more cohesive. Settling and compaction, crystallization, chemical reactions or adhesive bonding can cause such cohesion. These effects can be further influenced by the humidity and temperature of the environment, as discu.ssed previously. The powder may also experience adhesion if allowed to remain at rest against a surface, such as the steel of a container or a plastic bag liner. Adhesion can result in an increase in wall friction between the material and the surface, which can require hopper angles or external forces (e.g., vibration) to overcome the adhesion effects. 

The rate of hydration also causes changes in the microstructure. A slow rate causes a more distinct change toward a compact crystal shape. Citric acid addition causes a decrease in the total porosity and an increase in the average pore diameter. As a result gypsum strength was found to decrease with increasing additions of citric acid. 

Side chains must be absent or comparatively simple because, if they are bulky, they keep the main chains apart and prevent the formation of compact crystal structures. The effect of this is to separate the main chains from each other by a distance which is too great for the binding forces to come into play. This is well illustrated by the progressive methoxymethylation of nylon, as demonstrated in Table 2.1. 

For these photographs I am indebted to Dr. F. D. Chattaway. Transformation of the less stable needle-shaped crystals into the more stable compact crystals does not always take place spontaneously. Chattaway and Lambert state that needle-shaped crystals of 2 4-dibromoacetanilide in contact with alcoholic solution were kept for two years in a sealed tube, without transformation to the compact crystals taking place. 

The compact crystal form is prepared more safely by precipitating at room temperature a concentrated solution of mercury (II) nitrate or chloride with sodium azide. The product may be separated by centrifuging [12]. 

Triphenylphosphine fluorenone azine, (CeH5)3P=N—-C(CeH,)2, is the condensation product of triphenylphosphine and diazofluorene, but the action is much slower than with triethylphosphine. The product forms golden-yellow crystals, M.pt. 204° to 205° C. It may be kept for a month without decomposing, and may be recrystallised from alcohol without hydrolysis. On recrystallisation it yields yellow, compact crystals, M.pt. 209° to 210° C. When heated to 220° C. it suddenly evolves nitrogen. It is a much feebler base than the triethylphosphine derivative and it does not add on methyl iodide. It dissolves in dilute or concentrated hydrochloric acid, is insoluble in dilute sulphuric acid, but in concentrated sulphuric acid yields an orange-red solution, which, on dilution with water, deposits the base unchanged. It resembles the triethylphosphine derivative in forming an addition product with 2 molecules of hydrochloric acid. 

That rather extensive decomposition of silver nitrate can occur at activation temperatures only moderately above those which produce maximum activity is shown both by the rapid decline in diffraction intensity and by the increase in surface area which accompany higher activation temperatures, the latter effect being readily explainable as a result of the fragmentation of relatively compact crystals during thermal decomposition. The decrease in catalytic activity associated with these phenomena shows further that silver nitrate itself, and not its decomposition products, is the active component in these catalysts. This is... 

Description dark-metallic needles and plates, orthogonal, g 10 mm, distributed over the whole ampoule small amounts of P-Tel nutrient Te and a-Tel dark-metallic needles, sometimes with fibrous structure, partial sphe-rulites, S15mm, distributed over the whole ampoule nutrient Te and a-Tel dark-metallic compact crystals, bladed, often twins, g 3 mm, in direct contact with the nutrient (Te and a-Tel)... 

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