Precautions cyanides

The only important precaution in this preparation is to ensure an excess of zinc chloride over sodium cyanide. If the latter is in excess, the zinc cyanide generally precipitates as a sticky mass, which is difficult to filter and unsatisfactory for the preparation of hydroxy-aldehydes. 

Other sources of hazard arise from the handling of such chemicals as concentrated acids, alkalis, metallic sodium and bromine, and in working with such extremely poisonous substances as sodium and potassium cyanides. The special precautions to be observed will be indicated, where necessary, in the experiments in which the substances are employed, and will also be supplied by the demonstrator. The exercise of obvious precautions and cautious handling will in most cases reduce the danger to almost negligible proportions. Thus, if concentrated sulphuric acid should be accidentally spilled, it should be immediately washed with a liberal quantity of water or of a solution of a mild alkali. 

Isobutyronitrile (2-methylpropionitrile, isopropyl cyanide) [78-82-0] M 69.1, b 103.6 , d 0.7650, n 1.378. Shaken with cone HCl (to remove isonitriles), then with water and aq NaHC03. After a preliminary drying with silica gel or Linde type 4A molecular sieves, it is shaken or stirred with CaH2 until hydrogen evolution ceases, then decanted and distd from P2O5 (not more than 5g/L, to minimize gel formation). Finally it is refluxed with, and slowly distd from CaH2 (5g/L), taking precautions to exclude moisture. 

The properties of selected cyanides of industrial importance are summarized in Table 5.35. Depending upon scale of operation, precautions for cyanides include ... 

Following a published procedure for converting substituted anilines to isatins by reaction with chloral hydrate and hydroxylamine [1], it was noticed that at the end of the first stage (formation of an isonitrosoacetanilide), the odour of hydrogen cyanide was present, and this was confirmed by a Prussian blue test [2], In related work, concentrations of 100-200 ppm of hydrogren cyanide were found [3]. A mechanism for its formation from chloral hydrate and hydroxylamine was proposed [2], and the need for appropriate precautions was stressed [2,3],... 

In a 2-1. round-bottomed flask are placed, in the order mentioned, 50 g. (1 mole) of 98% sodium cyanide in 100 ml. of water, 58.9 g. (1.1 moles) of ammonium chloride in 140 ml. of lukewarm water (about 35°), and 134 ml. (2 moles) of aqueous ammonia (sp. gr. 0.90). The mixture is shaken while 120 g. (1 mole) of acetophenone in 300 ml. of 95% ethyl alcohol is added. The flask is stoppered with a rubber stopper, which is wired in place (Note 1), and is then immersed in a water bath maintained at 60°. The flask is shaken from time to time, and a homogeneous solution results within half an hour. The reaction mixture is heated for 5 hours at 60°, then well cooled in an ice-water mixture, and poured, with precautions (under a well-ventilated hood), into a 5-1. round-bottomed flask which is immersed up to the neck in an ice-water mixture and which contains 800 ml. of concentrated hydrochloric acid (sp. gr. 1.18-1.19). The reaction flask is rinsed with two 25-ml. portions of water, which are added to the hydrochloric acid solution. The solution of the aminonitrile is satu-... 

The reaction mixture, which becomes rather dark, is diluted with an equal volume of cold water and cooled to 0° or below. The solution is filtered, the precipitate is washed several times with ice water and then dissolved in 1600 cc. of boiling water. (A few grams of animal charcoal are added in dissolving the precipitate, if a technical -nitrobenzyl cyanide has been used.) This solution is filtered as rapidly as possible through a large folded filter, preferably with a steam funnel. In spite of all precautions, however, some solid usually separates on the filter. This must be redissolved in a minimum quantity of boiling water, and this solution then filtered into the main solution. The... 

Mettler et al. found that their original procedure was not very convenient for large-scale production of the malonate intermediate 16. Safety precautions required to handle excess solid potassium cyanide were both difficult and expensive. To compound the problem even further, a large amount of Ti02-pyridine complex was generated in the first step of this process. This solid waste material required special purification treatment before its final disposal. 

For the nitroprusside-cyanide reagent two solutions are prepared. For solution I, sodium nitroferricyanide (sodium nitroprusside, 1.5 g) is dissolved in 2M H2S04 (5mL) to which MeOH (95 mL) and NH4OH (10 mL) is added. A precipitate forms that is discarded. The clear, red solution is refrigerated. For solution II, sodium cyanide (2g) is dissolved in H20 (5 mL) and diluted with MeOH (95 mL), this is filtered if necessary. CAUTION Sodium cyanide can be absorbed through the skin and is extremely toxic. Appropriate safety precautions and first aid procedures should be adopted when handling sodium cyanide. 

Both hydrazine and hydrogen cyanide are toxic, and appropriate precautions should be taken. 

CAUTION Due precautions must be taken in handling potassium cyanide. 

Caution. Benzoyl cyanide is extremely toxic and should be handled with suitable precautions to prevent human contact. 

Sodium p-bromobenzenesulphonate, 550 Sodium carbonate - zinc mixture, 1042 Sodium cyanide, precautions in the use of, 409... 

It is important to observe in this process that the mcasuro in which the developer is mixed Bhould be chemically clean it ought, therefore, to be cleansed with cyanide of potassium, and well washed after every picture. In the ordinary wet process it is not absolutely necessary to take this precaution, although it is well to do so. The nitrate of silver added to the developer should be fresh solution, and not taken from the nitrate-bath. 

CAUTION Cyanide salts can be absorbed through the skin and are extremely toxic. Appropriate safety precautions and first aid procedures should be adopted when handling cyanide salts... 

CAUTTON Hydrogen cyanide (HCN) is produced as a toxic byproduct in the quenching of this reaction. Appropriate safety precautions and procedures should be employed. 

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