The Condenser for Distillation.

7. As a large quantity of ammonia-free distilled water is indispensable for the general purposes of analysis, an apparatus for

making it is advisable, although such water can be purchased, in glass-stoppered Winchester quart bottles, from the leading chemists.

It is possible to use the same type of condenser as is employed in the process of estimating the free and albuminoid ammonia in a sewage, but another condenser should be obtained, and used only for the production of ammonia-free distilled water.

The condenser devised by the author (Fig. 5) occupies very little space, and consists of a block-tin pipe, soldered within a copper pipe, water being circulated up between the two pipes. To make ammonia-free distilled water, a tin can is fitted with a semi-circular block-tin pipe, and is filled with 1,500 c.c. of good tap or spring water. A cork is fitted into the filling hole, and the tin pipe is fitted to the condenser. The can is then rested on a tripod, with a Bunsen burner underneath, and a stream of water passed upwards through the condenser. The distilled water is collected, and to successive 50 c.c. of it 2 c.c. of Nessler's test are added until no discoloration takes place, showing that the water is ammonia-free. With good tap waters this will be the case when 200 c.c. have been distilled off. The distillate is to be rejected until it shows absolutely no trace of ammonia. The distillation should be continued until a litre (1,000 c.c.) of ammonia-free water has been collected. In any case the distillation should not be continued after 1,200 c.c. of the original 1,500 c.c. have been distilled off, or the still may be injured.

Where a good public water-supply is available, it will frequently happen that the ammonia-free water may be obtained even in the first portion of the distillate. When this is the case, water may be supplied to the tin can continuously to replace the water distilled over, either by allowing water to drop into the hole at which the tin can is filled, or by the same arrangement by which it is suggested that the water-bath should be filled, namely, by inverting a bottle of water and feeding through the filling hole (see Fig. 6).

As soon as the water in the still falls below the level of the bottom of the glass tube through the cork, a bubble of air will be admitted into the bottle, and a small quantity of water will run into the still.

Before using the condenser for the preparation of ammonia-free distilled water, it should be washed out with good tap water, and after use the ends should be plugged with corks or cotton-wool to keep out the dust. The tin can should then be treated in the same

manner.

Where large quantities of distilled water are required Kent's stills will be found very convenient.

The Apparatus for the Albuminoid Ammonia Process.

8. The old way of conducting this process was extremely troublesome, but with the aid of the apparatus here described it can be completed in about half an hour. The use of a retort is dispensed with; it is no longer necessary to remove the flame at the end of

the first part of the process, and consequently the risk of breakage is reduced to a minimum. In addition to this, the apparatus is

exceedingly cheap, the only part which is breakable costing one shilling.

The condenser used (Fig. 7) is of the same pattern as that employed for making the distilled water. Instead of a retort in which to distil the water to be analyzed, a wide-necked Florence flask is

used, holding about 40 ounces. This is fitted with a good doublyperforated india-rubber bung. Before use the bung is boiled in a solution of caustic soda, to rid it of all traces of ammonia.

Through one perforation is fitted a piece of curved block-tin piping, the other end of which is made to taper so as to fit into the

FIG. 7.-APPARATUS FOR AMMONIA PROCESS.

tin pipe of the condenser. The second perforation is intended for a thistle funnel, into which is fitted a tapering glass rod.* The thistle funnel, as will be explained later, permits the alkaline permanganate solution to be poured into the flask after the free ammonia is distilled off, without it being necessary to turn down the flame, or to remove

*Fig. 7 does not show the glass rod plugging the thistle funnel.

the bung in the flask. The end of the thistle funnel should be partly sealed to make the permanganate run in a small, steady

stream.

Nesslerizing Glasses.

9. At least half a dozen 100 c.c. Nessler glasses are necessary. It will be found a great convenience to have one of these graduated in five parts, and tenths of a part, to be used for the standard solution of ammonia. Four of the Nessler glasses should be numbered consecutively, and risk of error will be reduced to a minimum by using them on the Nesslerizing stand, shown in Fig. 8. The Nessler glasses 1 and 2 are for collecting the free ammonia if it is to be estimated; numbers 3 and 4 are for collecting the albuminoid ammonia; the graduated tube is for making the standard solution, and the remaining tube is for making an additional tube of standard solution,

or for collecting more free ammonia if it does not all come off in the first 200 c.c. of distillate.

In the illustration the tubes are shown resting on the bottom of the stand instead of in the tapering holes above the opal glass. The bottom of the stand is covered with opal glass, so that the depth of the colour may be easily seen by looking down into it through the cylinder. When the tubes are not in use they should be swilled out with clean water and kept inverted on the stand.

Measuring Flasks and Cylinders, etc.

A large (2 litre) porcelain or enamelled iron dish is required for making the alkaline permanganate solution used for the albuminoid ammonia process.

10. A measuring glass with a lip, and marked at 50 c.c., is required to pour the 50 c.c. of the alkaline permanganate through the thistle funnel into the distillation flask after all the free ammonia