Mother liquor, defined

The sample is placed in a controlled environment to define the temperature state of the sample with a cooling cell (Bartunik and Schubert, 1982, Helliwell, 1985), or the state of the mother liquor with a flow cell (Hajdu et al., 1985). Pressure cells... 

Clear-liquor advance from what is called a double draw-off crystallizer is simply the removal of mother liquor without simultaneous removal of crystals. The primary action in classified-fines removal is preferential withdrawal from the crystallizer of crystals of a size below some specified value this may be coupled with the dissolution of the crystals removed as fines and the return of the resulting solution to the crystallizer. Classified-product removal is carried out to remove preferentially those crystals of a size larger than some specified value. In the following discussion, the effects of each of these selective removal functions on crystal size distributions will be described in terms of the population density function n. Only the ideal solid-liquid classification devices will be examined. It is convenient in the analyses to define flow rates in terms of clear liquor. Necessarily, then, the population density function is defined on a clear-liquor basis. 

Molasses, defined as the residual mother liquor from which little or no additional sugar can be recovered economically, is a byproduct... 

The first method of enantiomeric separation by direct crystallization is the mechanical technique use by Pasteur, where he separated the enan-tiomorphic crystals that were simultaneously formed while the residual mother liquor remained racemic. Enantiomer separation by this particular method can be extremely time consuming, and not possible to perform unless the crystals form with recognizable chiral features (such as well-defined hemihedral faces). Nevertheless, this procedure can be a useful means to obtain the first seed crystals required for a scale-up of a direct crystallization resolution process. When a particular system has been shown to be a conglomerate, and the crystals are not sufficiently distinct so as to be separated, polarimetry or circular dichroism spectroscopy can often be used to establish the chirality of the enantiomeric solids. 

Rapid cooling in an ice-water bath ( crash-crystallization ) usually produces small crystals occluded with mother-liquor, whereas slow cooling by allowing the collection flask to stand on the laboratory bench often produces large well-defined crystals. Remember to ... 

The impurity grid acts as a hypothetical model to define what could potentially form during the drug substance synthesis. Since any material from this grid which actually forms will be a PRI or in the mother liquors, these are the least important component of the KPSS. If any of the impurity grid substances are included in the KPSS, they may need to be synthesized. 

Methods of Crystallisation. — The crude solid product obtained directly as the result of a reaction is generally amorphous or not well crystallised. In order to obtain the compound in uniform, well-defined crystals, as well as to separate it from impurities like filter-fibres, inorganic substances, by-products, etc., it is dissolved, usually with the aid of heat, in a proper solvent, filtered from the impurities remaining undissolved, and allowed to cool gradually. The dissolved compound then separates out in a crystallised form, while the dissolved impurities are retained by the mother-liquor. (Crystallisation by Cooling.) Many compounds are so easily soluble in all solvents, even at the ordinary temperature, that... 

Some properties are more clearly defined than others. For example, solubility is defined as the amount of solid in equilibrium with the solvent. Solubility can affect the capacity of the crystallization process, as well as its ability to reject undesired compounds and minimize loss in the mother liquor. In addition, solubility varies widely from compound to compound or solvent to solvent. On the other hand, there are properties that are much less well characterized or understood. For example, the mechanism and condition for the formation of oil or amorphous solid remain unclear. The composition of oil and amorphous solid can be variable, and certainly can contain a much higher level of impurities than that in the crystalline solid, which leads to a real purification challenge. In addition, oil or amorphous solid generally is less stable and can create critical issues in drug formulation and storage stability. 

Crystals may be defined as solids composed of atoms arranged in an orderly repetitive array. The interatomic distances in a crystal of any definite material are constant and are characteristic of that material. Thus, for each chemical compound there are unique physical properties that differentiate that material from others, therefore, it is not unexpected that the formation of the crystalline material from its solution or mother liquor is accompanied by unique growth and nucleation characteristics. 

Better defined crystals are obtained if 67.4 g. of SnO (0.5 mole) is dissolved in 15-20 ml. of degassed water in a 200-mI.polyethylene beaker. The contents are heated on a steam bath to 60°C in an C -free nitrogen atmosphere and 46 g. of 48% hydrofluoric acid (1.1 moles) is added slowly and dropwise while the beaker is rotated. The reaction evolves heat. When all the solid is dissolved, the beaker is placed in a desiccator and cooled, so that crystals separate. After two hours, the mother liquor is decanted into a second beaker. Both beakers are then placed in a desiccator over a mixture of CaClg and KOH (1 1). After two days, this drying agent is removed and Mg (C10 )3 is substituted. After an additional four days, the mother liquor is again decanted and a second crop of crystals thus obtained. It is dried in the same manner as the first. The yield is 86%. 

Crystalline substances often form with water molecules located at specific sites in the crystal lattice, which are held in coordination complexes around lattice cations. This type of water is denoted as water of crystallization and is common for inorganic compounds. For example, nickel sulfate forms a well-defined hexahydrate, where the waters of hydration are bound directly to the Ni(II) ion. Extraneous inclusion of water molecules can occur if a coprecipitated cation carries solvation molecules with it. Water also can be incorporated into random pockets as a result of physical entrapment of the mother liquor. Well-defined multiple hydrate species can also form with organic molecules. For example, raffmose forms a pentahydrate. 

Solvent recovery and reuse—The reuse of organic solvents in a BPC system is widespread, especially given the increased cost of these materials and the environmental difficulties sometimes associated with their proper disposal. This reuse is achieved through defined procedures for the recovery of the solvents from distillates, extractions, and spent mother liquors. Where recovered solvents are utilized in the production of a BPC, the validation of the recovery process is strongly recommended. The validation of the recovery... 

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