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1. Be sure you understand the theoretical explanation (for which you may have to refer to other books) as well as the practical part of the experiment, or the reaction, which you perform.

2. Keep careful notes of each day's laboratory work, and write out answers to the questions found at the end of these pages.

3. One of the first virtues in the practical chemist is cleanliness. Learn to work neatly, and you will soon obtain exact views of the science. Those who work in a mess not unfrequently get their minds in a muddle.

H. E. ROSCOE. The OWENS COLLEGE, MANCHESTER,

October, 1872.

PREFACE TO THE SEVENTH EDITION.

To this edition I have added a series of examples on quantitative analysis, forming Part VI. of the book. I have chosen only such as are capable of easy and accurate determination, and trust they will serve as a sufficient introduction to the more complete study of the subject.

FRANCIS JONES. MANCHESTER,

August, 1882.

JUNIOR COURSE OF

LABORATORY

PRACTICE.

PART 1.

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PREPARATION OF APPARATUS,

GASES, &c. 1. Glass stirring-rods.

Divide a piece of glass rod into several pieces about iwo decimetres in length. This is done by filing the glass rod at each place where it is to be cut off, with a three-cornered file, and then snapping it across. Knock off any projecting pieces of glass which may be left at the newly-cut edges, and then hold each end of the rod in the flame of a Bunsen lamp until the sharp edges are fused and rounded. The glass rods thus made serve for stirring liquids, &c.

2. A wash bottle.

Soften a cork* by gently rolling it under the foot, and fit it air-tight into the neck of a flask about one litre capacity. Then, by means of a round file, bore two holes in the cork about three millimetres in diameter, * A doubly-bored india-rubber stopper may be used instead of a cork

B

and running parallel to each other and to the longer axis of the cork. Next obtain two pieces of glass tubing of the same diameter, one three decimetres long and the other half that length. Hold one end

of the longer tube in the Bunsen flame until the opening contracts considerably (but take care not to seal it up entirely), and then bend it about half a decimeter from the end, as shown in the figure. This is done by holding the glass tube horizontally in a common batswing gas jet flame, turning it round so as to heat all parts equally, and bending to the proper angle as soon as it feels sufficiently soft. Now round the edge of the wide

end of the tube by holding it in the flame till it softens, and when cold fit it into the cork. In a similar way round both ends of the shorter piece of tubing, bend to the angle shown in the figure, and fit into the other hole. Clean out the flask and tubes thoroughly, rinse with distilled water, and then fill up with distilled water.

3. Preparation of oxygen from mercuric oxide.

When mercuric oxide is heated it is decomposed into mercury and oxygen. Mercuric oxide yields mercury and oxygen.

Fig. I.

Hgo Hg + O
216 = 200 + 16

* For the explanation of these symbols a larger work must be consulted. See p. 13 of Roscoe's “ Elementary Chemistry.”

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