Crystals poisoning

The effects of trace concentrations of dissolved organic matter and of orthophosphates (Berner and Morse, 1974) and polyphosphates as "crystal poisons" (e.g., inhibiting the spread of monomolecular steps on the crystal surface by becoming... 

It is interesting to note that many crystal poisons not only interfer with nucleation and the growth of crystals but may also retard their dissolution. As we have seen (Chapter 6), precipitation and dissolution of solids proceed by the attachment or detachment of ions most favorably at kink sites of the crystalline surface. Solutes such as organic substances, or phosphates may upon adsorption immobilize kinks and thus retard dissolution. 

At the present time it is not possible to assign a precise function for any alkaline phosphatase. Undoubtedly bone phosphatase is concerned in ossification and two alternative roles have been proposed (1) Precipitation of calcium phosphate is induced by the localized production of high concentrations of Pi owing to phosphatase activity (33) (2) the enzyme permits crystal growth at nucleation sites in the matrix by ensuring the removal and continued absence of PPi which is known to be a crystal poison (60). Other factors must be involved (35) because tissues with high concentrations of alkaline phosphatase (e.g., gut, kidney, and... 

More recent studies have generally concluded that the inhibiting influence of Mg2+ results from difficulties in rapid dehydration of the Mg2+ ion, or from crystal poisoning by adsorption of Mg2+ at reactive sites. Mucci and Morse (1983) found that the log of the rate constant was a linear function of the solution Mg2+ to Ca2+ ratio and that the empirical reaction order increased from 3.07 to 3.70 as the Mg2+ to Ca2+ increased from 1 to 10.3. 

Fig. 26 Schematic view of the growth face of an extended-chain lamellar crystal poisoned by stems of half the chain length. The row-of-stems model can be applied with the row perpendicular to the growth face, as in the previous rough growth models to describe retardation of i (rowp), or parallel to the growth face to describe retardation of v (row q). (From [29], by permission of American Chemical Society)...

Trace concentrations of dissolved organic matter and orthophosphates and polyphosphates act as crystal poisons on the nucleation and growth of calcite probably by inhibiting the spread of mononuclear steps on the crystal surface by becoming adsorbed on active growth sites such as kinks. 

Although many biological fluids appear to be supersaturated with calcite, spontaneous mineralization does not occur. A number of explanations have been proposed, including the effects of crystal poisons and the high solubility of small crystal nuclei. An alternative approach to the problem is to suggest that there is an energy barrier which has to be overcome by the... 

White powder or crystals poisonous cardiac glycoside (g-strophanthin) from the seeds of the African trees Strophanthus gratus and Acokan-thera ouabaio. Used as a heart stimulant and by some African peoples as a dart poison. Blocks the Na+/K+-ATPase. 

Monohydrate, rhombic crystals. Poisonous, d 1,56. Sol in 25 parts water slightly sol in alcohol. 

Hemihydrate, hygroscopic crystals. Poisonous Converted to As20 by heating above 300°. Freely sol in water, alcohol, glycerol. LDM i.v. in rabbits 6 mg/kg, Joachimoglu, Bio-chem Z. 70, 144 (1915). 

Monohydrate, monoclinic prismatic crystals. Poisonous/ d 3.179. Loses its water of hydration at 120°, bagins to give off oxygen at 250°, mp 414°. Freely sol in water sol in hydrochloric acid moderately sol in ethylamine vety sparingly sof in ale, somewhat more in acetone. Practically insol in... 

Yellow, heavy, monoclinic, orthorhombic crystals. Poisonous/ d 4,50. Practically insol in water, dil acetic or chromic acids dissolved or dec by mineral acids. 

Dihydrate, crystals. Poisonous d 4.54. Loses S02 on heating above 150° forming BaS04. Sol in 4 parts water more so] in hot water slightly sol in alcohol. 

Crystals. Poisonous/ d 3.21. Soluble in 4 parts cold. 3 parts boiling water practically insol in alcohol. 

Monohydrate. crystals. Poisonous d 3.187. Sol in water practically insol in ale. 

Trihydrate, crystals. Poisonous/ Sol in water, methanol slightly sol in ethanol, ethyl acetate, acetone practically insol in ether,... 

Brownish-violet to black crystals. Poisonous d 3.77. Sparingly sol in water dec by alcohol. 

Crystals. Poisonous d 4.16. Practically insol in water sol in dil HQ ot HNOj. 

Deliquesc crystals. Poisonous) Very sol in water, sol in acetone, methanol, ethanol. Keep well closed. 

White to cream-colored powder, colorless or dark green orthorhomhic crystals, or dark red monoclinic crystals. Poisonous mp 474 . Practically insol in water, alcohol, cold dil acids sol in NH4OH dec by HNO,. boiling dil HCI. Sol in alkali cyanide solns because of formation of stable cyano-cuprateO) ions. 

Monohydrate colorless crystals. Poisonous/ d 5,53, Dec at ISO. Slightly sol in cold water moderately in hot water. 

Bitter crystals. Poison Somewhat deliquescent. Gradu -ally dec by light. One gram dissolves in about I ml water, in about 3 ml ethanol (95%), in 2 ml abs methanol. Practically... 

Barium salt, C,H,BaOgS,. barium methyl sulfate, Dihy. drate, efflorescent crystals. Poisonous So] in water, ale. 

Monohydrate, white, odorless crystals. Poisonous/ d 2.0. Sol in 40 parts cold, 6 parts boiling water, slightly in alcohol. pH of 0.1 molar aq soln 2.7. 

Dihydrate, violet, hygroscopic crystals. Poisonous/ Sol in water insol in alcohol, ether. Slowly dec in aq solns with formation Of the tel roxide. Keep well closed. 

Dihydrate, crystals. Poisonous/ Loses all its water over sulfuric acid or at 100". mp 281-284. Sol in about 60 parts water sol in alcohol or methanol, sparingly in acetone. 

White crystals. Poisonous d 7.1. mp 272. Soluble in 24 parts water, 3.7 parts boiling water insol in ale. 

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