30 Containment systems Curie

Potassium Phosphates. The K2O—P20 —H2O system parallels the sodium system in many respects. In addition to the three simple phosphate salts obtained by successive replacement of the protons of phosphoric acid by potassium ions, the system contains a number of crystalline hydrates and double salts (Table 7). Monopotassium phosphate (MKP), known only as the anhydrous salt, is the least soluble of the potassium orthophosphates. Monopotassium phosphate has been studied extensively owing to its piezoelectric and ferroelectric properties (see Ferroelectrics). At ordinary temperatures, KH2PO4 is so far above its Curie point as to give piezoelectric effects in which the emf is proportional to the distorting force. There is virtually no hysteresis. 

It is important to observe the applicability limits of the Curie-Weiss law and the implied physical meaning of the Weiss temperature It can only be applied to magnetic materials containing spin-only magnetic centers, and it only applies to magnetically condensed systems (as opposed to magnetically dilute systems) at sufficiently high temperatures fer>/ex). 

In protein analysis one important element is the purity of the enzyme and the procedure to obtain it. In many situations protein purification is not a simple step because of the lability of proteins. In many cases, the protein is associated with other components of the material from which it was obtained. As an example, the results for the analysis of the pyrolysate obtained from gluten at 510° C are discussed below. Gluten in this sample contained about 80% protein, 7% fats, and carbohydrates. The pyrolysis was first performed in a Curie point system and analyzed by on-line GC/MS on a Carbowax column in conditions similar to those previously described for the albumin analysis. The chromatogram is shown in Figure 12.3.5. 

In view of the wide application of Py—GC in industry and research, the development of techniques and equipment for automatic analysis by this method is of great practical interest. An automatic Py—GC system was developed by Coulter and Thompson [69] for Curie-type cells with a filament for specific application in the tyre industry. A typical analysis involves the identification and determination of polymers in a tyre material sample. The material of a tyre is essentially a mixture of polymers, most often natural rubber (polyisoprene), synthetic polyisoprene, polybutadiene and butadiene-styrene copolymer. A tube is normally made of a material based on butyl rubber and a copolymer of isobutylene with small amounts of isoprene. In addition to the above ingredients, the material contains another ten to twelve, such as sulphur, zinc oxide, carbon black, mineral oil, pine pitch, resins, antioxidants, accelerators and stearic acid. In analysing very small samples of the tyre material, the chemist must usually answer the following question on the basis of which polymers is the tyre made and what is their ratio The problem is not made easier by the fact that cured rubber is not soluble in any solvent. 

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