Лако-красочные материалы — производство

The dye chemist is frequently faced with the problem of preparing a new intermediate having a prescribed constitution and location of substituents. The solution of this problem is made much easier by an accurate knowledge of all of the laws governing the positions taken by substituents when they are introduced into the various aromatic ring […]

When a previously unknown compound has been made for the first time, the only criterion of its purity and homogeneity is the constancy of its properties after repeated purification operations. The compound is subjected to the various purification procedures (distilla­tion, recrystallization from as many different solvents as possible, conversion into salts, esters, amides, etc., and […]

It was pointed out in an earlier section that distillation in its various forms is generally the cheapest industrial method of purifi­cation. It is, of course, applicable only to those substances which can be volatilized without decomposition, and serves a useful purpose only if the impurities or by-products are sufficiently different in boiling point from […]

The acidic compounds, which react with bases to form salts, may be divided into three main groups: phenols, carboxylic acids, and sul­fonic acids. The phenols correspond to the aromatic amines. With caustic alka­lies, they give salts which are soluble in water without visible decom­position. Solutions of these salts, however, give a strongly alkaline re­action to […]

The aliphatic amines are, in general, volatile liquids soluble in water. They are strong bases which turn litmus blue, and react with mineral acids to form neutral salts. The reaction to litmus — apart from the phys­ical form — shows immediately whether the base or a salt is at hand. For the isolation and identification […]

Confronted with the isolation of an organic compound which has either acidic or basic properties, and which therefore forms salts, the beginner is often in doubt as to whether the compound should be iso­lated in its free state or in the form of one of its salts. Since the literature frequently contains little helpful information […]

This subject is discussed in the section entitled “Vacuum Distillation in the Laboratory and Plant” (page 341). 1. Steam Distillation Distillation with steam in plant operations is a relatively expensive process because it requires large volumes of steam and cooling water. For laboratory work, however, it is a very suitable method for the smooth separation […]

Distilling Off Solvents. In general, the solvent has a much lower boiling point than the product to be separated from it, and therefore a fractionating device is usually not required. There are, however, some substances which are volatile with steam and which are also carried over with the vapors of lower boiling solvents. In these […]

Distillation, if it is applicable, is the least expensive method for isolat­ing and purifying a reaction product. It is especially useful for: (a) removal of solvents, (b) purification of an already nearly pure reaction product (rectification), and, (c) separation of several reaction prod­ucts of different boiling points (fractional distillation). According to the type of procedure, […]

The precipitates commonly encountered in the analytical labora­tory are practically insoluble and can be washed with unlimited quan­tities of liquid. Organic products, on the other hand, are usually more or less easily soluble in the solvent employed, and hence it is always neces­sary to use the smallest possible amount of wash liquid which will com­pletely […]