Table of Contents
In most college laboratories and in some large industrial ones the sinks are located in the middle or at the ends of the work benches. In a small laboratory, however, it will be found more convenient to have a separate table for the sink and it will save plumbing to fit this table up for filtration by vacuum, distillations, etc.; in short for all the operations of the laboratory requiring water. Figure 7 shows such a table. It is 12 feet long and 3 feet wide. Its top is 33 inches from the floor. It is provided with a vacuum pump, a sink 3 x 2 feet, two water taps, a drain board, shelves for clean beakers and one for drying flasks, etc., water taps and waste pipe for condensers and for the still for furnishing distilled water, and gas taps for these latter.
Lab Sinks
The sink is placed four feet from one end of the table, leaving a space of table of this length on the right, for filtrations by vacuum; and on the left for drying beakers and for standing apparatus to be washed, etc.
The sink itself may be of galvanized iron, zinc or enameled iron. The latter is to be preferred. Wood also makes a very good sink, but it is hard to make one out of it which does not leak. The writer at one time had a large wooden sink, 4 ft. x 3 ft., in his laboratory which gave excellent service. In order to prevent drying and consequent leaking, the waste pipe was so arranged as to keep about an inch of water in the bottom of the sink all the time. The usual objection to metal sinks is the corrosion due to acids, and the fact that glassware must be carefully handled around them, as a very light tap against the bottom of a metal sink is sure to result in a broken beaker or flask. A sheet of corrugated rubber matting or a small rubber door mat laid in the sink will save much apparatus. Underneath the sink is as good a place as any for a large stoneware jar in which to pour waste acids and filter papers. This jar is to be emptied daily by the janitor and, if used, will save; many plumbers bills for renewing the waste-pipe.
As the sink table is 3 feet wide and the sink is but two, the latter should be so placed in the former as to be about four inches from the front of the table. This space, before and behind, should be boxed up and the edges of the boards, lapping over the sink, nicely rounded. In the drawing, the waste-pipe is shown straight without the usual S-shaped trap. When the waste-pipe does not lead into the same sewer as the toilet room, this trap can be omitted; and, if it is done, will save repairs, as acids are almost sure to find their way into the sink and, if the acid water lies in the bend of the trap, it will in time eat a hole in this. Lead is to be preferred to iron for the waste-pipe as the less readily attacked by acids.
Water Taps
In the illustration of the sink table a peculiar form of water tap is shown over the sink. This is one made by Thos. Saville, Philadelphia, Pa. An ordinary lever tap may also be used. The advantage of this form is that the water can be turned on full with a single motion of the hand or shut off equally easily. It will be found of advantage to place a few inches of rubber tubing on the end of at least one of the taps. This not only permits the stream of water being directed in any direction but if the force of its flow from the tap is considerable it deadens this somewhat. The taps should stand at least six inches forward of the rear end of the sink and their tips should be about 18 inches from the bottom.
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Drying Apparatus
A board for drying beakers, etc., should be located to one side of sink. In the table shown, this board is 2 ft. x 3 ft., extending all the way across the table. It is corrugated like a wash board, all the grooves radiating from the sink so as to drain the water into this. Above the board are shelves for clean dry beakers. If thought desirable, these can be made into a cupboard by adding doors. Above the sink is a shelf bored with holes of various sizes for drying flasks, pipettes, etc., as shown in the cut.
Casseroles are much used in some iron and steel laboratories in place of beakers. For drying these, a board with pegs, inclined about 150 from the vertical, placed behind and so as to drain into the sink, will be found useful. The pegs should be in pairs, in a row, and placed so that the casserole, laying face to the board, handle downward, has a peg on each side of the handle. The pegs should be about four inches long and the rows should be no nearer together than the diameter of the greatest casserole in use. Each pair of pegs should be the same distance apart as the rows, and the individual pegs of the pair should be about 1½ or 2 inches apart.
The sink table as illustrated is provided with drawers and is boxed up to form a closet for storage of apparatus. To prevent trash, etc., being brushed into the latter when the floor is swept, the floor of the closet should be at least 3 inches above that of the room.
The top of the table may be of wood, stone, slate, concrete or sheet lead. Two-inch white pine board makes a good cheap top. When this becomes acid scarred it can be covered with oilcloth or the boards turned, exposing the lower surface, or renewed entirely. The desk itself should be filled and varnished or primed and painted. The top, however, if of wood should not be treated in any way but should be left just as it is.
It is well to have on the water line, somewhere easily accessible, a valve with about five or ten feet of good garden hose, with nozzle attached, for fire protection. This will be found cheaper than the hand grenades and equally serviceable for putting out small fires.