The most important of the inorganic materials are cement and stoneware.

Where complete resistance to acid is required, stoneware is the only material which can be used. Occasionally, indeed, its place may be taken by lead, but, as every works chemist finds out in course of time, even with the most careful lead-lining, expensive repairs become necessary sooner or later. If a plant has to be used for an indefinite length of time without interruption, stoneware must be used or, very occasionally, acid-resistant stone, such as volvic lava, granacite, or Binger sandstone.

For smaller-sized plant, taps made of stoneware are much used, and with careful treatment they will last indefinitely. They are liable, however, to be damaged by hot liquids owing to cracking; they must also be carefully lubricated to avoid sticking. The so-called armoured stoneware cocks are more resistant to shock and heat; the outside consists of lead-lined tin-plate which is usually tightened up by means of a screw, so that by loosening the latter slightly the tap is readily removed. These armoured taps have quite replaced the older type made of hard lead (lead-antimony). Stoneware is also used for piping, centrifuges and valves. The baskets of stoneware centrifuges are placed inside a steel basket to prevent them flying to pieces owing to the centrifugal force. Some of the pieces of apparatus made are very complex, but we cannot go further into this question here; details will be found in the catalogues issued by the stoneware manufacturers.

Stoneware reservoirs are much used which are either made in one piece or built up from separate pieces. Complete vessels may be prepared up to 5000 litres capacity, but they are very sensitive to slight variations in temperature and are also expensive. Acid-resistant tanks can be constructed in the factory if a good bricklayer is available: an iron pot is covered with a layer of cement, and when this is dry a layer of acid-proof bricks, or glazed stoneware plates, is fixed to it by means of ordinary cement. The individual plates must be set 6 mms. apart from one another; the resultant grooves are filled up with acid-proof cement, which is obtainable in excellent quality from various firms. The grooves are first half-filled with the aid of a thin wooden spatula, and the cement is dried by heating the whole apparatus with a steam coil, which takes about 14 days. Only when the first layer of the acid-proof cement is quite dry are the grooves completely filled up and again dried. The complete preparation of such a tank holding 5000 litres takes about 2 months. When the cement has set, the vessel is filled with 2 % sulphuric acid and allowed to stand for three days. By this means the acid-proof cement is hardened, and there is no danger of the grooves developing leaks. When properly prepared, such a vessel will withstand even hot 80 % sulphuric acid, and can be guaranteed to stand pressure and vacuum. Vessels are also made with two layers of acid-proof tiles in which the grooves are so arranged that the first set of grooves are covered by the second tiles. They are, however, very expensive, and last hardly any longer than a tank with a single layer when properly made.

Alkaline and neutral liquids may be kept in cement reservoirs which are frequently reinforced with iron. As enormous tensions are developed on heating, the reinforcing must be carefully calculated. Cement vats are also used for the manufacture of colours, but it is advisable to line such vats also with acid-proof tiles as even quite weak acids rapidly corrode the cement. Cement stirrers can also be made and are very useful in special cases.

The floors of works sheds may be covered with a layer of acid-proof tiles cemented together with sulphur; this adheres firmly to the tiles and is not, like asphalt, washed away by hot water. In sheds where the floor keeps dry a good cement surface is sufficient.

Glass, owing to its brittleness, is used relatively little, but often there is no alternative. For chlorinations at high temperatures, for instance, it is indispensable (see also Dichlorbenzaldehyde). Tubing for conveying chlorine is often of glass, and glass stirrers are met with fairly frequently which are made by fixing stout glass rods into an iron or wooden beam. Fused quartz is little used as yet, but quartz lamps are coming into favour for chlorinations (cf. p. 93).

Porcelain is only found in laboratories and dye-houses. The much vaunted resistance glass vessels burst too frequently to be worth recommending.

Enamel is a particular form of glass which is specially used for coating cast iron. The production of a good acid-proof enamel is no easy matter, and for works plant a double coating is often applied. This enamel has not so good an appearance as the enamel used on ordinary household articles, but it is much more durable. An enamelled apparatus which has developed a defect at any point must practically always be dismantled, for which reason it needs to be treated with great care. Enamelled vessels must never be touched with metal instruments but only with wooden implements. Very complicated pieces of enamelled apparatus are made, which are charged for according to their weight and are very expensive. Enamelled ladles and pots are also much used.