CHAPTER XXI

LABORATORY PRACTICE

Object of Laboratory Practice, Laboratory Note-book, and Suggestions for Laboratory Practice.—The aim of the laboratory practice is to give the students an idea of the composition, uses, and values of food materials, and the part which chemistry takes in sanitation and household affairs; also to enable them by simple tests to detect some of the more common adulterants in foods.

Before performing an experiment, the student is advised to review those topics presented in the text which have a bearing upon the experiment, so that a clear conception may be gained of the relationship between the laboratory work and that of the class room. The student should endeavor to cultivate the power of observation and to grasp the principle involved in the work, rather than do it in a merely mechanical and perfunctory way. Neatness is one of the essentials for success in laboratory practice, and too much emphasis cannot be laid upon this requisite to good work. The student should learn to use his time in the laboratory profitably and economically. He should obtain a clear idea of what he is to do, and then do it to the best of his ability. If the experiment is not a success, repeat it. While the work is in progress it should be given undivided attention. Care should be exercised to prevent anything getting into the sinks that will clog the plumbing; soil, matches, broken glass, and paper should be deposited in the waste jars.

Fig. 72.—Apparatus used in Laboratory Work.
See page [301] for names.

A careful record of the experiments should be kept by each student in a suitable note-book. It is suggested that those students desiring more time in writing out the experiments than the laboratory period affords, take notes as they make the various tests, and then amplify and rearrange them in the evening study time. The final writing up of the notes should, however, be done before the next laboratory period. Careful attention should be given to the spelling, language, and punctuation, and the note-book should represent the student's individual work. He who attempts to cheat by copying the results of others, only cheats himself. In recording the results of an experiment, the student should state briefly and clearly the following: