AN IMPROVED APPARATUS FOR TESTING THE QUALITY OF MILK AND OTHER SUBSTANCES.
Year: 1877

page_text: PROVISIONAL SPECIFICATION left by William Robert Lake at the Office of
the Commissioners of Patents on the 2nd January 1877. A communication
from abroad by Doctor Louis Heusner, of Barmen, Prussia.
"
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent Agents,
Southampton Buildings, London. AN IMPROVED APPARATUS FOR TESTING THE
QUALITY OF MILK AND OTHER SUBSTANCES.", A communication from abroad by
Doctor Louis Heusner, of Barmen, Prussia.
This Invention relates to an improved milk tester or lactometer, which serves for
detecting adulteration of milk with water as well as the removal of cream, and
which will also serve for testing other substances. The said apparatus consists of
two parallel circular plates of glass, which are cemented or rivetted or otherwise
attached to a metal plate of suitable thickness to leave a space between the said
plates of glass on both sides of the metal plate. By this metal plate the space
within the plates of glass is separated into two distinct halves. On the inner side
of one of the two plates of glass I provide, by burning in or otherwise, crossed
black lines, or certain words may be used instead of the lines, as for example,
"Dr. Heusner's Patent Milk Test," which lines or words are of the same dimensions
and are arranged in the same manner on both halves of the plate. These lines or
words shine through sharp and black on the back of the apparatus.
When the apparatus is used for testing milk I provide within one of the halves
of the dividing space a small plate of semi-transparent or opal glass or porcelain,
which possesses exactly the same transparency as milk in its normal state when in
a layer corresponding with the diameter of the dividing space. By covering this
small plate of semi-transparent or opal glass or porcelain with an oil paper corre-
sponding in color or with a similar piece of glass or other suitable material, the said
plate of semi-transparent or opal glass gives the peculiar yellow tinge of milk. The
covering will be on the side on which the same lies nearest to the burnt in lines or
words. The lower division of the apparatus when seen from the back therefore
appears yellow under the black lines. On the front side of the apparatus the black
lines or words on the lower division appear dim if the apparatus is held up to the
light, because they are covered by the semi-transparent or opal glass or porcelain and
the oil paper.
Instead of the small plate of semi-transparent or opal glass or porcelain other
substances may be made use of, which are suitable to imitate milk in color and

page_text: transparency, such as condensed milk, butter, yellow wax, stearine, soap, or any
other suitable material.
In order to use the apparatus as a milk tester the same is dipped into the milk
which is to be tested after the stoppers provided thereon have been partly with-
drawn from the empty space; after the space has become filled with milk the same
is closed with the said stoppers. The apparatus is then wiped on the outside and
held up towards the light, the glass plate with the black lines or the words being
held away from the eye. If the crossed lines or the words show through the milk
half (the upper half) more distinctly and sharper than through the glass half (the
lower half) then the milk under test is either watered or skimmed. But if, on the
contrary, the lines of the upper half appear precisely as feeble as those of the lower
half, then the milk is in its normal condition.
I purpose to adapt this apparatus for the testing of all alimentary fluids, such as
wine, beer, and medicines; which are subject to adulteration.
The normal substances serving for the comparison must, however, consist of
corresponding substances in nature (so far as the same can be made use of), or of
an imitation of the same by colored glass, porcelain, fluids, or solid materials
of any kind whatever, which are suitable to imitate the colors and transparency
required.