Stabilising Agent

Thiourea was used as stabilising agent for zerovalent Pd species [117]. The Pd-thiourea (H2NCSNH2) catalysed carbonylation of terminal alkynes and allylic alcohols has been described by Chiusoh [118]. More recently, Pd-thiourea-catalysed carbonylative annulation was studied. The reaction proceeds between alkynes, iodophenol acetates and carbon monoxide, in the presence of dppp, thiourea (H2NCSNH2) and base at 40 °C. Flavones have been obtained in good yields (Scheme 30) [119]. 

The main function of the foam stabilising agent is to reinforce the intercellular film wall by contributing rheological characteristics of viscoelasticity. The increased viscosity may also assist handling. The aim, as so often with auxiliaries, is to achieve an optimum balance. If the bubbles are too thin and wet too quickly they will collapse prematurely, whilst too stable a film could hinder uniform application. Examples of products used as foam stabilisers include thickening agents such as the polysaccharides, hydroxyethylcellulose, methylcellulose,... 

Chen G, Jiang Y et al. The mood stabilising agent valproate inhibits the activity of glycogen synthase kinase 3. J Neurochem 1999 72 1327-1330. 

A pale yellow solid, the main protein in milk. It is used as a stabilising agent in latex compounding. Casting... 

This mechanism may account for the stability, in the absence of any external stabilising agent, of amphiphilic homopolymers in the fully collapsed/glo-bular state. The total free energy of a collapsed macromolecule includes a surface energy contribution in addition to the bulk free energy. Obviously, to form a stable particle, the outer shell of the particle should be hydrophilic enough. 

Most of the facts in Sections 2.2.1 to 2.2.10 are actually sufficient to dispose of this view and, taken together, they form an array of concordant and compatible observations which are all incompatible with it. In addition, it must be noted that amongst reagents of the type which interest us here, equilibria between ions and esters are unknown, and that attempts to prepare some of the active esters, e.g., styryl triflate, in the absence of a stabilising agent, always produce intractable mixtures [49]. 

Food colours Flavours and sweeteners Fat emulsifiers and stabilising agents Flour improvers - antistaling agents and bleaches Antioxidants Preservatives... 

In the processing context, a combination of mechanical forces and chemical reactions (oxidation, etc.) deactivates enzymes. It should be noted that there is at present no systematic way of improving the stability of an enzyfhe. Each system has unique properties and stabilising agents must be selected in an empirical fashion. 

Adsorbed layers of stabilising agent may cause a significant lowering of the effective Hamaker constant and, therefore, a weakening of the interparticle van der Waals attraction. This effect has been considered by Void207 and by Vincent and co-workers208 in terms of the Hamaker microscopic treatment of dispersion forces. 

In certain cases, colloidal dispersions are made more sensitive to aggregation by the addition of small quantities of materials which, if used in larger amounts, would act as stabilising agents. Several factors may contribute to such observations ... 

Soluble substances like iodine also act as emulsifiers, in the case of ether/water emulsions. Some mixed stabilising agents also act as emulsifiers, e.g., ethyl alcohol and lycopodium powder, acetic acid and lamp black, clay and sodium oleate etc. 

Section V Stabilising Agents Recommended none are recommended Tolerated citric, tartaric, malic, ascorbic, fiimaric acids from nonsynthetic sources according to BATF standards. Low temperatures for tartrate stabilisation (cold stabilisation). Flash pasteurisation with technical justification Prohibited potassium ferrocyanide, synthetic citric acid, metatartaric acid, sorbic acid and sorbates... 

There is interest in trace metal levels in both natural and synthetic fibres and fabrics but perhaps most interest is in synthetic fibres as these may contain residues of catalysts, treatments or stabilising agents. Reviews have been published of trace-metal analysis of rayon, polyamide, polyester and polypropylene fibres [178] and of cotton fabrics, especially for flame... 

An aqueous solution containing 34 to 38% w/w of CH2O, with methanol as a stabilising agent. 

---