Please address all communications, answers to questions, etc., to Alfred E. Forstall, Secretary, Room 22, 58 William Street, New York City, and put on the envelope your name and address. January, 1901.

ANSWERS TO FIRST SERIES OF QUESTIONS, 1901-SECOND SECTION-PRACTICAL CLASS-AMERICAN GAS LIGHT ASSOCIATION.

The answer to Question No. 12 has been published in Vol. XVI of the Proceedings, page 59, and can be found there. The answers to the other questions are as follows:

1. What tests would you apply to a fire brick to determine its quality?

Ans. The qualities desired in a fire brick are: infusibility, strength, regularity of shape, uniformity of composition and facility of cutting, and the tests to be applied to a fire brick should be such as will determine to what extent it possesses these qualities.

The degree of infusibility can be determined, to a certain extent, by an analysis of the material of which the brick is composed. If this analysis shows the presence of about 60% of silica, less than 6% of sesqui-oxide of iron and not more than 2% to 3% as a total of lime, magnesia and the hydrates of potassium and sodium, the brick probably possesses a high degree of infusibility. If the analysis shows more than 6% of sesqui-oxide of iron or 2% to 3% of the lime, magnesia, etc., the brick should be rejected. But exposure of the brick to the action of heat under the conditions to which it will be subjected when used furnishes the best test for infusibility. In coal gas works the test can be made by placing the brick in the combustion chamber of a regenerative bench. If, when the brick is removed after being exposed for a week or ten days to the heat of the combustion chamber, the edges and corners are found to be sharp, and the surfaces show no signs of incipient fusion the brick may be passed as of first rate quality, as far as infusibility is concerned. In water gas plants the space at the bottom of the superheater, in which the secondary combustion occurs, furnishes a good place for a test.

If the material of which the brick is made is well compressed during manufacture and the brick is hard burned there is no question as to its strength when cold. The degree to which compression has been carried is indicated by the weight of the brick, and

a fire brick of the regulation size, 9′′ × 41⁄2′′ × 25%", should weigh from 74 to 71⁄2 lbs. A well burnt brick usually shows a reddish tinge. A well compressed and well burnt brick will give a ringing sound when struck with a hammer. It is especially important that the bricks which are to be used for lining the furnaces of retort benches, or for lining water gas generators, should be hard, since they are subjected to a great deal of abrasion from the fuel and the clinkering bars, so that for this work hardness and strength are of more importance than infusibility. In the combustion chamber, on the contrary, infusibility is the most important quality, since the material used there is not exposed to any wear and tear except that arising from the effect of the heat It may thus frequently happen that the same brick is not suitable for use both in the furnace and the combustion chamber.

An examination of the exterior of the brick is all that is necessary to determine whether or not it possesses regularity of shape.

Uniformity of composition can be tested by breaking the brick and examining the surface of the fracture. This should present a compact and uniform appearance though not necessarily a close and fine texture. In fact some authorities consider a coarse texture the more preferable. Uniformity of composition is also indicated by the giving out of a clear ringing sound when the brick is struck a sharp blow with a hammer..

Facility of cutting is important only as reducing the cost of labor and the amount of waste during the operation of laying the brick, and while desirable if it can be secured without sacrificing the more important qualities it cannot be considered an equivalent for any one of them. (Trustees.)

2. What are the precautions that should be taken in laying fire brick and fire clay blocks, to secure for the finished work strength and the ability to resist heat?

Ans. The principal precautions to be taken in laying up fire bricks or fire clay blocks are that the bricks, or blocks, should be well wetted just before they are laid in place, and that each brick, or block, should be rubbed into place in such a way as to bring its faces almost into contact with the faces of the adjacent bricks, or blocks, in the wall, the joints being made as thin as it is possible to have them and at the same time have the fire clay fill all the interstices so as to give a uniform bearing over the whole surface.

This is especially important in the case of arches, which should be laid as nearly as possible with the blocks face to face. Bricks and small blocks can be wet by dipping them into water in a bucket, kept filled and at hand for the purpose, each piece being. dipped by the mason as he picks it up for the purpose of laying it in place in the wall. The surfaces of large blocks should be wet by having water sprinkled on them, a convenient method being to employ for the sprinkling a whisk broom which is wet by being dipped into the water in the bucket. The portion of the work previously laid, upon which the bricks, or blocks, are to be placed, should also be wet in the same way.

To secure thinness of joints, those surfaces of the blocks which come together should be smooth plane surfaces, being dressed to this condition if they do not originally possess it, and the fire clay must be mixed thin rather than stiff, care being taken not to get it so thin that it will run out of the joint, nor so stiff that any excess will not be squeezed out when the block is worked into place. If the joints are not made thin the fire clay will soften and run out of them when the work is subjected to heat, or even if it does not do this it will shrink under the action of the heat and cause a settlement of the upper part of the brick work.

Another precaution which should be observed is that when it is necessary to cut bricks or blocks the cut surfaces should never be exposed to the direct heat of the fire, the face so exposed being always one which has not been cut. (Trustees.)

3. Describe-with sketches giving a vertical cross section, a vertical longitudinal section and a horizontal longitudinal section showing the nostrils in the furnace arch, the secondary air openings into the combustion chamber, and the openings through which the hot waste gases pass into the recuperators—a setting of six retorts heated by a generator furnace and equipped with recuperNeither furnace nor recuperators need be illustrated except to the extent required to show the above mentioned openings. Ans. The regenerative setting of six retorts, which is illustrated by the accompanying sections, is designed to be built in an arch 8'-4" wide and to contain retorts, the inside measurements of which are 15" x 26" x 9'-0".

ators.

As will be seen from the cross section, the combustion chamber is made wide and high, being 14" wide and 3'-6" from the top of the furnace arch to the bottom of the first arch of the setting

which crosses the combustion chamber. The producer gas enters this chamber by five openings, or nostrils marked N, spaced equal distances apart from front to back along the centre line of the bench. The secondary air is admitted through the openings marked S. A. There are five of these on each side of the combustion chamber, level with the top of the furnace arch, each nos

Bench of 6 Retorts. Regenerative Setting.

Vertical Longitudinal Section.

tril having a secondary air opening opposite it on each side so that two streams of secondary air are directed against each stream of producer gas.

The setting is built in one single chamber, the combustion taking place and the hot gases passing up around the retorts along the full depth of the bench. To secure effective heating of the bottom of the bottom retorts small passages, which lead out of