Third. Magnesia, or chlorides of magnesium, at 324° and 364°.
It is to take advantage of this fact that mechanically arranged jets, sprinklers and long perforated pipes are introduced into the interior of a steam boiler; these tend to scatter the depositing impurities and also to bring the feed water more quickly to the highest possible temperature.
Where fuel is expensive and pumps are used for continuous service under high and unusually high pressures it is oftentimes advisable to operate the pumps condensing. This may be done, when the pump lifts water by suction, without a separate condenser by connecting the exhaust pipe with the suction pipe, as shown in Fig. [667]. Assume that the pump has been working properly for from 3 to 5 minutes with the valve A nearly closed and the valve B a little open, the valve A is now quickly closed and B opened. In operating these valves both hands should be used, so that they may be opened and closed simultaneously.
Fig. 667.
So penetrating is water at high pressure that only special qualities of cast iron will be tight against it. In the early days of the hydraulic jack it was no uncommon thing to see water issuing like a fine needle through the metal, and the water needle is said to penetrate the flesh as readily as one of steel.
The engraving, Fig. [668], represents a novel device for preventing the bursting of water pipes by freezing. This is simply an air chamber placed in the horizontal part of the pipe, with the chamber on top side so that the ice may expand into this chamber, and so its force is expended upon the air instead of bursting the pipe.
This device also acts as an air chamber and prevents “water hammer.” It is made by the Anti-bursting pipe Co., Pittsburg, Pa.