Crystal growth, control

For instance in azo pigment manufacture, the crude product is given some form of surface treatment, such as with rosin, to control crystal growth, control aggregation and to aid in dispersion. 

Figure 1-11 Concentration profile for (a) crystal growth controlled by interface reaction (the concentration profile is flat and does not change with time), (b) diffusive crystal growth with t2 = 4fi and = 4t2 (the profile is an error function and propagates according to (c) convective crystal growth (the profile is an exponential function and does not change with time), and (d) crystal growth controlled by both interface reaction and diffusion (both the interface concentration and the length of the profile vary).

Nucleation is necessary for the new phase to form, and is often the most difficult step. Because the new phase and old phase have the same composition, mass transport is not necessary. However, for very rapid interface reaction rate, heat transport may play a role. The growth rate may be controlled either by interface reaction or heat transport. Because diffusivity of heat is much greater than chemical diffusivity, crystal growth controlled by heat transport is expected to be much more rapid than crystal growth controlled by mass transport. For vaporization of liquid (e.g., water vapor) in air, because the gas phase is already present (air), nucleation is not necessary except for vaporization (bubbling) beginning in the interior. Similarly, for ice melting (ice water) in nature, nucleation does not seem to be difficult. 

The air cell stabilizing effect of agglomerated fat globules, promoted by emulsifiers and the ice-crystal-growth-controlling effect of hydrocoiloid stabilize the foam structure of ice cream to a great extent. This is evident by melt down analysis (see section 5.2) of ice cream exposed to heat shock. 

Uses Emulsifier, dispersant and wetting agent used in alkaline cleaning formulations antigelling agents, automotive radiator cleaners, metal, cement, brick, and tile cleaners for crystal growth control plastics, rubber latex stabilizer... 

Synonyms Naphthalenesulfonic acid, bis-(1-methylethyl)-, sodium salt Empirical CieH2oNa03S Properties M.w. 315.39 anionic Uses Emulsifier, dispersant and wetting agent used in alkaline cleaning formulations antigelling agents, automotive radiator cleaners, metal, cement, brick, and tile cleaners for crystal growth control plastics, rubber latex stabilizer Trade Name Synonyms Rhodacal BA-77 t[Rhodia HPCII http //www.rhodia-hpcii.com, Rhodia HPCII France... 

Sodium dodecyl diphenyl ether disulfonate cleaner, tile crystal growth control Sodium isopropyl naphthalene sulfonate cleaner, toilet bowl Methoxy PEG-40 Methoxy PEG-100 cleaner, waterless hand Cetoleth-6 cleaner, window lsotrideceth-7 cleaner, wood Potassium acid oxalate cleaner, zinc-base die-cast metals Ammonium thiosulfate cleaning agent, metals Hydrochloric acid cleaning compound mfg. 

Tailor-Made Additives for Crystal Growth Control... 

TAILOR-MADE ADDITIVES FOR CRYSTAL GROWTH CONTROL... 

Berkovitch-Yellin, Z. Toward an ab initio derivation of crystal morphology, J. Am. Chem. Soc. 1985,107,8239-8253. The statement, coming from one of the founding members of the Weizmann school on crystal growth control, presumably refers to tailor-made impurities, but nevertheless sounds as a mourning bell for all theories of crystal formation based only on static energies and classical thermodynamics of pure systems. 

Chem. Descrip. Microcrystalline cellulose and cellulose gum USP/NF CAS 9004-34-6 9004-32-4 EINECS/ELINCS 232-674-9 Uses Fat replacement, mouthfeel enhancer in foods stabilizer in low-fat emulsions foam stabilizer, ice crystal growth control agent, syneresis inhibitor, vise, builder, opacifier, particulate suspending agent in frozen desserts, whipped toppings excipient, vehicle, vise, control agent, thixotrope for pharmaceutical suspensions and emulsions... 

Functional properties are high sweetness (r.s. 120-180), synergistic sweetening effects, flavor enhancement, moisture management, crystal growth control, browning reaction and freezing point depression. F. and its syrups are mainly used in food and pharmaceutical industries, in the latter for infusion fluids, for parenteral nutrition forms, and for health and sports dietetics. 

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