178. The wash-bottle described (68) is of my own contrivance. Kustel describes one, made from an acid-carboy, arranged like that which I have described for the working test. Deetken used simply the bell glass, standing in an open basin of water, with leaden pipes for the introduction and eduction of the gas, passing under the edge of the bell. This arrangement would seem liable to upsetting. I used one in which the bell was secured vertically, in a tub of water, by means of a cross board fixed in the tub, with a hole to fit the bell. The gas was introduced by a leaden pipe, passing under the bell, and escaped through the neck of the latter, with which a rubber pipe was connected.

The objection to a bell standing in an open vessel containing water is, that the water becomes saturated with chlorine, which is constantly evolved from the exposed surface. This, though not important in a well ventilated room, may produce inconvenience in closer quarters. The carboy is less convenient than the barrel for the renewal of the water, besides being liable to accidental breakage. So, on the whole, I think that my contrivance is to be preferred. The barrel will be the better for being tarred inside; better still if coated with paraffin.

If there is any difficulty in finding a bottle which will admit the chlorine pipe through the neck, it will answer to pass the pipe through the head of the keg. The gas will find its way to the bell, and, if the keg is full of water, the bubbling of the chlorine will be as visible as if it were delivered immediately under the bell, which, however, must be set higher than in the figure in this case, unless the pipe be of lead, and curved so as to deliver under it.

It is not essential that the gas should be seen to pass, because it can always be heard bubbling through the water, so that a glass bell is not absolutely required, but it is convenient, enabling one to see that the proper quantity of water is in the keg.

The water should be renewed once in two or three weeks, and that which is drawn out can be utilized in making the precipitant for gold from scrap iron.