An Introductory Course of Quantitative Chemical Analysis | Page 4

remembered that a close concordance of results in "check analyses" is
not conclusive evidence of the accuracy of those results, although the
probability of their accuracy is, of course, considerably enhanced. The
satisfaction in obtaining "check results" in such analyses must never be
allowed to interfere with the critical examination of the procedure
employed, nor must they ever be regarded as in any measure a
substitute for absolute truth and accuracy.
In this connection it must also be emphasized that only the operator
himself can know the whole history of an analysis, and only he can
know whether his work is worthy of full confidence. No work should
be continued for a moment after such confidence is lost, but should be
resolutely discarded as soon as a cause for distrust is fully established.
The student should, however, determine to put forth his best efforts in
each analysis; it is well not to be too ready to condone failures and to
"begin again," as much time is lost in these fruitless attempts. Nothing
less than !absolute integrity! is or can be demanded of a quantitative
analyst, and any disregard of this principle, however slight, is as fatal to
success as lack of chemical knowledge or inaptitude in manipulation
can possibly be.
NOTEBOOKS
Notebooks should contain, beside the record of observations,
descriptive notes. All records of weights should be placed upon the
right-hand page, while that on the left is reserved for the notes,
calculations of factors, or the amount of reagents required.
The neat and systematic arrangement of the records of analyses is of
the first importance, and is an evidence of careful work and an
excellent credential. Of two notebooks in which the results may be, in

fact, of equal value as legal evidence, that one which is neatly arranged
will carry with it greater weight.
All records should be dated, and all observations should be recorded at
once in the notebook. The making of records upon loose paper is a
practice to be deprecated, as is also that of copying original entries into
a second notebook. The student should accustom himself to orderly
entries at the time of observation. Several sample pages of systematic
records are to be found in the Appendix. These are based upon
experience; but other arrangements, if clear and orderly, may prove
equally serviceable. The student is advised to follow the sample pages
until he is in a position to plan out a system of his own.
REAGENTS
The habit of carefully testing reagents, including distilled water, cannot
be too early acquired or too constantly practiced; for, in spite of all
reasonable precautionary measures, inferior chemicals will occasionally
find their way into the stock room, or errors will be made in filling
reagent bottles. The student should remember that while there may be
others who share the responsibility for the purity of materials in the
laboratory of an institution, the responsibility will later be one which he
must individually assume.
The stoppers of reagent bottles should never be laid upon the desk,
unless upon a clean watch-glass or paper. The neck and mouth of all
such bottles should be kept scrupulously clean, and care taken that no
confusion of stoppers occurs.
WASH-BOTTLES
Wash-bottles for distilled water should be made from flasks of about
750 cc. capacity and be provided with gracefully bent tubes, which
should not be too long. The jet should be connected with the tube
entering the wash-bottle by a short piece of rubber tubing in such a way
as to be flexible, and should deliver a stream about one millimeter in
diameter. The neck of the flask may be wound with cord, or covered
with wash-leather, for greater comfort when hot water is used. It is well
to provide several small wash-bottles for liquids other than distilled
water, which should invariably be clearly labeled.
TRANSFER OF LIQUIDS
Liquids should never be transferred from one vessel to another, nor to a
filter, without the aid of a stirring rod held firmly against the side or lip

of the vessel. When the vessel is provided with a lip it is not usually
necessary to use other means to prevent the loss of liquid by running
down the side; whenever loss seems imminent a !very thin! layer of
vaseline, applied with the finger to the edge of the vessel, will prevent
it. The stirring rod down which the liquid runs should never be drawn
upward in such a way as to allow the solution to collect on the under
side of the rim or lip of a vessel.
The number of transfers of liquids from one vessel to another during an
analysis should be as small as possible to avoid the risk of slight losses.
Each vessel must, of course, be completely washed to insure the
transfer