"O. The condenser is the most important part of the machine, excepting perhaps the pump (G). On the proper construction of the condenser depends not only the safety of those working in its vicinity, but to a great extent the purity and quality of the water produced. It is therefore of the greatest importance that no pains should be spared to secure the best possible materials and workmanship in this part of the work. The material of the condenser is the best gun-metal, or in some cases hammered copper. This gives the requisite strength to withstand the great internal pressure, and it is thoroughly tested before being set to work. It is in the form of an elongated sphere, and is put together in two halves very accurately fitted and secured by strong gun-metal flanges connected with "bolts and nuts. This arrangement enables the halves to be easily taken apart for cleaning or re-tinning, and is in all respects the most thoroughly practical that can be made. The whole of the interior is very carefully tinned with the best English tin; found practically equal, if not superior to silvering, but we undertake the latter process at a small extra charge when customers desire it". It is in the condenser that the water becomes carbonated by pressure and agitation. For the latter purpose an agitator is constantly kept revolving inside, while the condenser is being charged with gas and water. The spindle of the agitator passes through a stuffing-box, and is supported at its outer end by a suitable bracket. The front end of the spindle is also supported in a stuffing-box, and at both ends the water is kept from all contact with the working parts by cup leathers. Any metal which may be worn off the spindles, escapes outside by a suitable channel; there is, therefore, complete security against contamination from the metal worn off the ends of the spindle.

Every machine is provided with the pressure-gauge, on which is marked the pressures at which to bottle the various carbonated water generally used. By means of this gauge the bottler cannot only see that the pressure continues uniform, but there is also clearly marked on the dial the pressure at which it is best to bottle the various carbonated liquids. The condenser is also provided with an efficient safety valve. It has sometimes been recommended to carry a pipe from the safety valve to the gas holder to convey back the gas that escapes; this is found by experience to require caution, as the water which is pumped into the condenser contains a large amount of atmospheric air. This air being lighter than the gas collects at the top of the condenser, and is the first to escape through the safety valve. In course of a short time this air will spoil the quality of the gas in the gas holder, unless special arrangements are made.

A great advance has been made of late years in recognizing the importance of a large condenser for the more complete carbonating of the charge contained in it. A large condenser naturally takes rather more time to charge at the beginning of the day's work, but when once charged it needs neither more time nor power to keep it charged. On the other hand it will be evident to every one who thinks over the subject that in a large condenser the water has much more time to become thoroughly carbonated than in a small one. Let us suppose that the bottling goes in at the rate of 30 bottles a minute, and that the condenser only holds the contents of 15 bottles, it is evident that the average stay of the water in the condenser is only half a minute. Now let us suppose that instead of this condenser we substitute one four times as large, holding 60 bottles, leaving the size of the pump, etc., exactly the same. It will be seen that the water will on an average remain in the condenser two minutes. Now this time of staying in the condenser represents the time during which the water is exposed to the full pressure of gas and is being mixed with it by means of the agitator. It will not be too much to say therefore that we may expect the water in the latter case to be nearly four times as well carbonated as in the former. It will therefore be seen that those machines which have a large condenser possess a great advantage over those with a small one.

The gas-and-water pump may be' termed the vital part of the machine, as the carbonating process entirely depends on its efficient working. It is arranged in the way already mentioned in describing Bramah's machine. The plunger works upwards from below, being kept tight by a cup leather placed in a gland at the bottom; this cup leather becomes tighter as the pressure increases. The valves for admission and delivery of the gas and water are at the top of the pump, placed in a suitable valve piece. Each cock is provided with an index, showing on a metal quadrant the exact distance it is open.

Fig. 75.   Carbonating Machine with Double Beam Action

Fig. 75. - Carbonating Machine with Double Beam Action.

This double-beam-action machine, manufactured by the same makers as the last one, has two extra large gun-metal cylinders, each of which is connected with its respective pump, with all the requisite fittings to make it perfect. Each condenser is provided with a water and pressure-gauge, the former to show the height of the water, and the latter to indicate the exact pressure. The condensers hold a large quantity of water; and it is the opinion of many soda-water makers that the presence of a large volume of water in the condenser facilitates the production of soda water of uniform strength. The united machines can be worked together or separately; moreover, one of the cylinders can be supplied with solution of soda, while the other is receiving plain water, so that the manufacture of soda water and the manufacture of lemon-soda or any other kind of carbonated water may be carried on simultaneously.

A larger and different machine is represented in the following cut (Fig, 76). This machine is very highly to be recommended for large factories. The great size of the condensers ensures the perfect carbonation of the water, and the pumps are very powerful. The arrangement is peculiar for its great compactness and strength, being suited for very heavy work, and for bottling at high pressure. The two pumps and condensers may be worked either together or separately; and it is worth notice that one condenser may be used for makmg soda water, while the other is supplied with pure water for lemon-soda, so that the manufacture of both drinks can go on simultaneously. The machine is provided with pressure-gauges, water-gauges, and every requisite.