Perchloric acid precautions with

Precaution Combustible exposed to heat or flame forms sensitive explosive prod, on reaction with perchloric acid incompat. with strong oxidizing agents may be sensitive to prolonged exposure to air keep away from food... 

Attention is drawn to the hazards involved in the use of perchloric acid in a published method [1] for transesterification of triglycerides with methanol. Alternative acid catalysts and safety precautions are suggested [2],... 

The rapidity with which sulphuric acid decomposes potassium chlorate is well known. If small quantities of the salt are treated with the acid, with the precaution of fusing the salt in the retort and, when cold, pouring sulphuric acid on the mass, the violence of tho reaction is rednced, and, at a convenient temp., a gas is disengaged which can be collected over mercury, and which is designated deutoxide of chlorine. The residue in the retort contains potassium sulphate, and sparingly soluble unknown salt of a new acid (perchloric acid). 

The dehydration of lanthanide perchlorates to obtain the anhydrous salt has been studied [13-15]. Lighter lanthanide perchlorate lose the water of hydration readily at 200°C under vacuum while the heavier lanthanide salts produced insoluble basic salts. Anhydrous heavier lanthanide perchlorates have been obtained by extraction with anhydrous acetonitrile. Utmost precaution should be exercised in the purification of lanthanide perchlorate, since the mixture of lanthanide perchlorate and acetonitrile can lead to an explosion. An alternate approach involves the addition of triethylorthoformate to the mixture or refluxing the solvent through a Soxhlet extractor packed with molecular sieves [3], In view of the hazardous nature of perchlorates, alternate materials such as lanthanide trifluoromethane sulfonates have received some attention. Lanthanide triflates are thermally stable, soluble in organic solvents, unreactive to moisture and are weak coordinating agents. Triflic acid is stronger than perchloric acid [17]. Lanthanide perchlorates and triflate have the same reduction potentials in aprotic solvents and the dissociation of the triflates is less than the perchlorates in acetonitrile [17],... 

The precautions needed flow naturally from the properties in addition to the precautions usual when handling any strong acid, it is necessary to ensure that perchloric acid does not come into contact with easily oxidisable organic matter or strongly reducing substances under circumstances where it can become hot or anhydrous. It is failure to observe these precautions that leads to problems, and a few examples of what to do and what not to do are given below —... 

Having stressed some of the precautions to be taken, it is perhaps necessary to list the advantages of using perchloric acid, with particular reference to its use in wet oxidation procedure. 

Alternatively, the following perchloric acid procedure can be used. Perchloric acid can be used on inert (glass or quartz fiber) filters or with filters where a pretreatment has oxidized most of the organic material. In no event should reactive organic compounds be in contact with fuming (hot, concentrated) perchloric acid, nor should perchloric acid be fumed without an adequate fume trapping system or the use of a perchloric acid hood. This procedure is not suitable for preparation of samples to be analyzed by ETA. For proper safety precautions refer to Perchloric Acid and Perchlorates by Schilt [15]. 

This procedure is recommended for materials that are decomposed by attack with HF and HC104. (See also the section in Chapter 3 giving precautions to be taken when using perchloric acid.)... 

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