by means of special apparatus to heat the cold water for steam boilers. Sulphuric acid is delivered into an overhead acid tank, and by means of suitable pipe and tap is led to the saturator. Here the ammonia gas, coming from the top of the still, is intimately mixed with the acid which, in a short time, begins to precipitate a salt in the form of sulphate of ammonia. The resulting salt is then fished out by means of ladles or steam elevators on to the drainer, which is constructed so that the liquid can run back into the saturator.

When the sulphate is sufficiently dry, it is thrown into the sulphate store which is constructed so that any further drainings will flow to the mother liquor well.

The mother liquor is used up again in the saturator.

APPENDIX.

THE REFEREES' SULPHUR TEST.

HE apparatus employed in this test is shewn in Fig.

TH

64, and consists of a Bunsen burner a, with steatite top in which the gas to be tested is burnt, the burner being mounted on a short cylindrical stand, provided with a series of holes for the admission of air, and having on its upper surface a deep circular channel or groove, in order to receive the wide end of the glass trumpet-shaped tube B, which is connected to a glass cylinder c, filled with marbles and having a glass chimney tube E, at the top, for the purpose of affording a vent for the uncondensable vapours, and also to create a draught for the necessary air required. The inlet of the burner is connected to the outlet of an experimental meter capable of automatically shutting off the gas when ten cubic feet have been burnt. The apparatus is used in the following manner. The stem of the burner is surrounded with pieces of sesqui-carbonate of ammonia. The burner is then lit, and when the index of the meter is close to zero, the trumpet tube is placed in position on its stand, and its narrow end connected to the tubulure of the condenser, the long chimney tube being simultaneously attached to the top of the condenser. The burner is to be regulated to consume half a cubic foot per hour, so that it will take twenty hours to make a test; at the expiration of which time the meter will automatically cut off the supply of gas to the burner. After each testing, the vessel placed

underneath the condenser to receive the products of combustion is to be emptied into a measuring cylinder, and then replaced to receive the washings of the condenser. The trumpet tube is next removed and well washed out, the resulting washings being added to the contents of the measuring cylinder. The condenser is then treated with

B

E

FIG. 64.

forty or fifty c.c. of distilled water, and these washings also added to the previous contents of the measuring cylinder; after which the whole of the liquid in the cylinder is well mixed and then divided into two equal parts, one portion being reserved for future reference if required. The remaining half of the liquid is now placed in a glass beaker, covered with a large watch glass, acidified with hydrochloric acid, and then gently raised to the boiling point. An excess of a solution of chloride of barium is then added

and the boiling continued for five minutes. The beaker and its contents are then allowed to stand until the barium sulphate settles at the bottom of the beaker, after which as much as possible of the clear liquid is poured on to a Swedish filter paper, and after this has passed through, the remaining liquid and barium sulphate are similarly treated, the contents of the filter being well washed with hot distilled water, until a small quantity of the final washings

FIG. 65.

remain clear on adding a drop of a solution of nitrate of silver. The filter and its contents are then dried, and transferred into a weighed platinum crucible, which is gradually heated to redness until no black particles remain ; it is then allowed to cool, and when nearly cold, placed in a desiccator over strong sulphuric acid and weighed again. The difference between the first and second weighings of the crucible will give the number of grains of barium sulphate. This weight multiplied by eleven and divided by four will give the number of grains of sulphur in 100 cubic