stated: the "water" of the generator may admittedly be safely maintained in the fluid state, but from so cold a liquid acetylene will not be generated smoothly, if at all. Moreover, were it not so, a process of this character is unnecessarily expensive, although suitable salts are very cheap, for the water of the generator is constantly being consumed, [Footnote: It has already been said that most generators "consume" a much larger volume of water than the amount corresponding with the chemical reaction involved: the excess of water passing into the sludge or by- product. Thus a considerable quantity of any anti-freezing agent must be thrown aside each time the apparatus is cleaned out or its fluid contents are run off.] and as constantly needs renewal; which means that a fresh batch of salt would be required every time the apparatus was recharged, so long as frost existed or might be expected. A somewhat different condition obtains in the holder of an acetylene installation. Here, whenever the holder is a separate item in the plant, not constituting a portion of the generating apparatus, the water which forms the seal of a rising holder, or which fills half the space of a displacement holder, lasts indefinitely; and it behaves equally well, whatever its temperature may be, so long as it retains a fluid state. This matter will be discussed with greater detail at the end of Chapter III. At present the point to be insisted on is that the temperature in any constituent of an acetylene installation which contains water must not be permitted to fall to the freezing-point; while the water actually used for decomposition must be kept well above that temperature.