Decomposition by heat

For further purification the material may be recrystallized from hot water, or dissolved in alkali and reprecipitated, or distilled under reduced pressure or sublimed. Each of these operations involves considerable loss of product, either through solubility or through decomposition by heat. The best-appearing product is obtained by distillation under reduced pressure. The crude acid is distilled from a Claisen flask with a delivery tube set low in order that the acid need not be heated much above the boiling j)oint. The product boiling at i4i-i44°/20 mm. is ])ure wliitc and melts at 125-132° (Note 8). The yield of distilled acid is about 75-85 per cent of the weight of the crude acid. 

Carbon dioxide and calcium carbonate The effect of carbon dioxide is closely linked with the bicarbonate content. Normal carbonates are rarely found in natural waters but sodium bicarbonate is found in some underground supplies. Calcium bicarbonate is the most important, but magnesium bicarbonate may be present in smaller quantities in general, it may be regarded as having properties similar to those of the calcium compound except that on decomposition by heat it deposits magnesium hydroxide whereas calcium bicarbonate precipitates the carbonate. 

Tyrosine, tryptophan and tetracyline are filter-sterilised to prevent decomposition by heat sterilisation. 

Up to about 70 C, plant tissues are thermally stable, as they must be in nature to avoid damage from prolonged direct exposure to the sun. Pyrolysis, the chemical decomposition by heat, starts in dry lignocellulosics around 100 C, in moist ones below 80 C. It accelerates as temperature rises, peaking in many organic materials between 275 and 300 C, at which point cellulose disintegrates. 

Sulfonium compounds undergo elimination similar to that of their ammonium counterparts (7-6 and 7-7) in scope and mechanism. The decomposition by heat of sulfonium hydroxides has been known for many years.218 The ylide reaction was discovered more recently.219 Neither is important synthetically. 

According to the classical work of Abel [3] the instability of nitrocotton samples is caused not so much by the tendency of nitrocellulose to decompose, as by the presence of certain impurities. Abel showed that the purest nitrocellulose was so resistant to decomposition by heating that it could withstand the action of a temperature between 65 and 100°C even for several months. He also demonstrated that low-nitrated cellulose added to guncotton does not exert an adverse effect on the latter s stability and its capacity to withstand the heat test. 

Many of the reactions of nitroguanidine, particularly its decomposition by heat and the reactions which occur in aqueous and in sulfuric acid solutions, follow directly from its dearrangement.13 Nitroguanidine dearranges in two modes, as follows. 

Hansen LD, Lewis EA, Eatough DJ, Bergstrom RG, DeGraft-Johnson D. Kinetics of drag decomposition by heat conduction calorimetry. Pharm Res 1989 6 20-27. 

Platinum Native, and as speriylite (PtAs2) Dissolution of native Pt in aqua regia, precipitation as (NH4)2PtClCatalyst adsorbent for gases manufacturing jewelry, electrical instruments, electrodes, crucibles, etc. 

Hansen, L.D., Lewis, E.A., Eastough, D.J., Bergstrom, R.G., DeGraft-Johnson, D. (1989). Kinetics of drug decomposition by heat conduction calorimetry. Pharm. Res. 6,20-27. 

Explosive decomposition by heating or by explosive shock is the basis for its use as an explosive ... 

Paneth22 first demonstrated that the decomposition by heat of certain organic compounds furnished products which removed metallic mirrors of silver, tellurium and other metals from the walls of the tube. For example when vapor of lead tetraethyl was heated a silver coating on the inside of the exit tube was removed for a considerable distance. The results were interpreted to mean that ethyl radicals were liberated in the thermal decomposition and... 

In the last-named case the reaction is dangerously explosive and should only be carried out with small quantities of the reagents. Ozone is also formed during the decomposition by heat of potassium chlorate, and by the action of nitric acid, preferably of density 1-33, on ammonium persulphate1 carefully warmed up to 65° to 75° C. The liberated gases are washed with caustic-potash solution and contain from 3 to 5 per cent, of ozone. 

Decomposition by heating a substance in the presence of a catalyst and in the absence of air. 

Thus, Heuser took up the alcoholates of cellulose, its esters, its ethers, and the oxidations of cellulose which led to carbonyl groups and to carboxyl groups. But he also had an important chapter on the hydrolysis and the acetolysis of cellulose, on its decomposition by heat, and its degradation by bacteria. His final chapter, on the constitution of cellulose, was largely historical in nature, and, viewed from present-day knowledge, it was, perhaps, less successful than were some of the others. But the entire little volume was conceived from a logical viewpoint—one that was very welcome to those of us who had tried to cope with some of the older literature. The book was relatively brief and very clearly written. 

These reactions must be distinguished from homolytic decomposition by heat and LfV light that break the 0—0 bond by energy deposition, yielding alkoxyl and hydroxyl radicals ( OH). The 0—0 in organic hydroperoxides (BDE = 25-38 kCal/mole) begins decomposing at about 50°C and is completely decomposed at 160°C (297). 

Like phosgene, as in the decomposition by heat or in presence of aluminium chloride thus it reacts with dimethylaniline forming Crystal Violet. ... 

The reverse of some of the above reactions may be seen in the decomposition by heating, perhaps in oxygen, of polyatomic non-metallic cations which have been ion exchanged into the zeolite, or which were present as templates from the synthesis. These include the ammonium, hydronium, and alkylammonium ions. In all cases, the final products are hydrogen ions. Depending upon the temperature and the zeolite, these may leave with oxide ions of the zeolite fi-amework as water vapor, so that the fiamework which remains is deficient in oxygens. 

In the decomposition by heat other acids are also formed, viz., ita-conic and citra-conic acids (p. 293). In this case both carbon di-oxide and water are lost. 

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