The chief feature of the Mondollot system is, that it entirely dispenses with the gasometer. In other respects it is the same in principle as the old Bramah system, although in the working details improvements or alterations have also been made, and the chief difference lies in the arrangement of the apparatus for generating the carbonic acid gas, while the mechanical portion for pumping the gas and water together under strong pressure remains identical in action. Mr. Mondollot, formerly of Paris, late of London, has been succeeded by H. Favarger, London.

In the Mondollot machine the carbonic acid gas is drawn from the generator without the medium of the gasometer, the pump itself being made to regulate the quantity of sulphuric acid that is admitted to the carbonate, and it is claimed with such accuracy, that every stroke of the pump draws into the generator the exact amount of sulphuric acid that will replace the carbonic acid gas that has just been drawn out by the very same stroke.

The gasometer is not used to store the carbonic acid gas. The gas is said to be purified on its way from the generator to the pump, and to be effected in all these machines' by two purifiers, through which the gas is drawn in small quantities at each stroke of the pump. One of the purifiers is always of glass; this gives the operator the means of seeing how the purification is going on, and also whether the pump is in proper working order. As said before, the pump itself regulates the supply of sulphuric acid to the generator, and thus avoids the service of the acid tap, and, it is claimed, prevents the generator requiring any attention from the time the materials are put into it until they become exhausted.

Another important fact in connection with this machine is said to be that all possible explosion is prevented by an ingenious safety water valve, which consists of a U-shaped tube, which rises from the top of the generator and which is filled with water. If the pressure in the generator exceeds that of the atmosphere, the water is thrown out, leaving a clear passage for the escape of the gas, and at once gives notice to the operator that something is going wrong.

The manufacturers give the following descriptions of their apparatus : "In all our machines the foundation or body is composed of one solid casting, on which are cast, and not bolted, all brackets, projections, and angle pieces, to which are attached the various working parts. This ensures a perfectly level bearing for the main shaft, which thus runs with a minimum of friction, and requires less power to drive it. The shaft, crank, and connecting-rod are of the best forged iron, and are all turned bright. The crank is at the end of the shaft, and works the piston by a connecting-rod made in one solid forging. The fly-wheel is very large and heavy. The saturator is of great thickness, and is made of hammered copper, which is a guarantee against explosion, as this metal would rend in the event of an accident, but would never burst and fly to pieces. It is thickly coated inside with block tin, thus ensuring freedom from metallic contamination. It is spherical in shape, the only opening being placed at the base. This opening is closed by a cover, which is placed inside the saturator, in the style of an internal stopper, and makes a perfectly tight joint, for the greater the pressure internally, the closer the joint.

"The agitator is composed of four powerful pans, heavily tinned, and is firmly carried in a tubular bracket, which is securely bolted in the saturator. This tubular bracket serves as a stuffing-box, and the washers in it are so disposed as to close up and make a tighter joint as the pressure increases inside the saturator. This arrangement of working the agitator in a tube packed with washers effectually prevents contamination of the water, as the metal working parts never come in contact with each other. A simple contrivance allows a single nut placed outside the driving cog-wheel to tighten up the packing inside the tubular bracket. All the pipes of the machines are of copper, heavily lined with tin. The purifiers are made, one of glass, and the other of copper tinned. The pump is of gun-metal, the plunger being made of specially hard and close-grained material so as to prevent the possibility of its conveying air into the saturator, as is the case with a plunger of a spongy or defective metal. The cup leather is of the usual shape, but is made to cling (irmly and closely to the plunger by means of a rubber ring carefully adjusted to it. The valves are of gun-metal tinned, and have seatings that never require grinding in, and if, after many years work, they require renewing, it is a plain and simple matter to exchange them for fresh ones. The valve 16 box is of easy access, two bolts and nuts only holding it together, so that in the busy time there is never any delay in changing valves when necessary.

"Fig. 136 is a machine which was specially designed for very small makers. It is constructed for using bicarbonate of soda and flute sulphuric acid. The crank and shaft are turned bright. The generator is made of chemically pure lead, so as to resist the action of the sulphuric acid. The machine is sent out ready for working, and requires no fixing beyond being firmly bolted to the floor.

"Fig. 137 is a view (partly sectional) of the gas generator or producer.

Fig. 136.   Mondollot Machine, No. 0

Fig. 136. - Mondollot Machine, No. 0.

Fig. 137.   Sectional View of Generator in Fig. 136

Fig. 137. - Sectional View of Generator in Fig. 136.

S is a cylindrical vessel open at the top, for containing sulphuric acid. Within this vessel is fixed a second cylinder C of smaller diameter by greater length. A false bottom divides the interior of this cylinder into two compartments, the upper of which is for receiving the bicarbonate of soda. It is an open tube pierced with holes for nearly the whole of its length, and it is fixed in the centre of the false bottom. B is a tubular opening for charging the cylinder C with the bicarbonate, b is a portion of the tube connecting the apparatus with the condensing and pumping machine, and d d is a flexible tube for discharging the acid and water.