METHOD OF AND APPARATUS FOR DETERMINING THE QUANTITY OF FAT IN MILK
Year: 1885

page_text: I, CARL GUSTAF PATRIK DE LAVAL, M.A. of No 14 Alandsgatan, Stockholm,
Sweden, Civil Engineer, do hereby declare the nature of said invention for
"METHOD OF AND APPARATUS FOR DETERMINING THE QUANTITY OF FAT IN MILK'
to be as follows:-
"
The want of a good testing apparatus for milk, that is, one which combines with
handiness and simplicity, rapidity of operation, has made itself much felt,
particularly in great dairies collecting their milk from many different farms. The
apparatus hitherto in use for testing milk are of little real use, as they either
indicate the percentage of cream of the milk, which does not stand in any
fixed relation to the percentage of fat, or they are difficult of management and
complicated.
The principal value of milk, at least for dairies, is the butter fat contained
therein; therefore milktesting apparatus to be of real service should be arranged
to indicate the amount of this fat.
.
By apparatus according to this invention the percentage of fat in the milk can
be determined with a great rapidity and with so great an accuracy, that it competes
with the chemical analysis. Besides that, the method is so simple that an unskilled
person can make the tests.
The principle of this new method of testing milk is to separate from a certain
quantity of milk the butter fat it contains, the volume of which is afterwards read.
In order to get this fat separated free from caseine, the latter must be dissolved.
As dissolving agent a mixture of acetic acid and sulphuric acid is used. A certain
quantity of this mixture is added to a certain quantity of the milk to be tested;
and afterwards the whole is brought to a suitable temperature, and is poured into a
vessel provided with a fine tube of glass. This vessel either alone or together with
other similar vessels, is introduced in a centrifugal apparatus, and by means of the
centrifugal force the fat is forced into the tube, where the volume is read. Or
after the treatment with acetic acid and sulphuric acid, the fat may be left to rise
without any assistance in a Chevalier's cream glass for instance, but the testing
operation takes then more time and the result is less certain than by using the
centrifugal operation.

page_text: In one form of apparatus according to this invention the test-vessel consists of a
cylindrical silvered metallic box, into which a silvered metallic stopper or plug fits
accurately. This plug is turned and bored hollow from the bottom tapering
towards the top into a fine hole communicating with a fine glass tube either
graduated or not graduated. This glass tube is fixed upon the plug by a nut,
screwed into a socket or holder and the nut is provided with a hole so that the
plug and the tube constitute conjointly a vessel or channel, open at both ends.
One or more of these test vessels are placed in recesses in a plate or whirling
table mounted on a vertical rotating shaft driven by power, and the milk under
treatment is then subjected to centrifugal action, the testing process being conducted
as follows:-
Into a common test-tube equal volumes of the milk to be treated and of the
above mentioned mixture of acetic acid and sulphuric acids are introduced. The
mixture which has been found most suitable is composed of 20 volumes of
concentrated acetic acid and 1 volume of concentrated sulphuric acid. The test-
tube, closed by a cork perforated by a small tube of glass, is agitated a little and
then heated on a water bath during 5 to 10 minutes, after which it is agitated
very vigorously.
The cork is now taken out of the test-tube and the contents are poured into one
of the above described boxes until it is full.
The plug belonging to the box is then pushed in so far as it will go. The little
test-vessel will then be completely filled and the surplus gets away through the
hole in the nut, and thus an accurately measured quantity of fluid is obtained.
The test-vessel is then pushed, the box foremost, into one of the holes in the plate
or whirling table. In like manner the other specimens to be tested are similarly
prepared. The holes in the plate must previously to the introduction of the test-
vessels be filled with hot water of 50° Cels; or more. The hotter the water is
the more the heat of the plate is conserved. Its temperature should be at least
50° Celsius.
All the test vessels having been introduced, a lid is put on for the purpose of
preventing refrigeration. The apparatus is then put in motion with a speed of
about 6000 revolutions a minute during 3 to 5 minutes. After stopping the
apparatus the test-vessels are taken out and the volume occupied by the fat
column in the glass tube is immediately read. The fat being in a melted state
appears quite transparent and clear, but a determined limit can however be
observed between the fat and the solution of caseine existing beneath. It occurs
frequently that a little white plug of casëine is visible between the fat and the
acid solution. This seldom exceeds the tenth part of a millimetre in length. If
the milk is not diluted by water, this plug does not present itself, or only traces
thereof are to be seen. The graduations are preferably arranged in such way that
of the number of divisions occupied by the separated fat, just indicates the
percentage of the fat contained in the milk. For instance if 33.5 divisions are
read, the milk contains 3.35% of fat. The reading can very well be carried
to 0-2 division and thus there occurs an error only of about 0.02 %, say an error
of 0.5% of the weight of the butterfat in milk of 4 per cent. As 12 tests can be.
made by this apparatus in 10 minutes (the heating of new tests takes place during
the testing of the preceding ones) the great rapidity of 72 tests an hour has been
attained, and these as accurately made as by means of chemical analysis.

page_text: Fat in Milk.
I, CARL GUSTAF PATRIK DE LAVAL, M.A. of N° 14 Alandsgatan, Stockholm,
Sweden, Engineer, do hereby declare the nature of my invention for "METHOD OF
AND APPARATUS FOR DETERMINING THE QUANTITY OF FAT IN MILK " and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement :-
The want of a good testing apparatus for milk, that is, one which combines
with handiness and simplicity, rapidity of operation, has made itself much felt,
particularly in great dairies collecting their milk from many different farms. The
apparatus hitherto in use for testing milk are of little real use, as they either
[indicate the percentage of cream of the milk, which does not stand in any fixed
relation to the percentage of fat, or they are difficult of management and
complicated.
The principal value of milk, at least for dairies, is the butter fat contained
therein; therefore milktesting apparatus to be of real service should be arranged
to indicate the amount of this fat.
By apparatus according to this invention the percentage of fat in the milk can
be determined with a great rapidity and with so great an accuracy, that it
competes with the chemical analysis. Besides that, the method is so simple that
an unskilled person can make the tests.
The principle of this new method of testing milk is to separate from a certain
quantity of milk the butter fat it contains, the volume of which is afterwards read.
In order to get this fat separated free from casëine, the latter must be dissolved.
As dissolving agent a mixtnre of acetic acid and sulphuric acid is used. A certain
quantity of this mixture is added to a certain quantity of the milk to be tested,
and afterwards the whole is brought to a suitable temperature, and is poured into
a vessel provided with a fine tube of glass. This vessel, together with other such
vessels, is introduced in a centrifugal apparatus, and by means of the centrifugal
force the fat is forced into the tube, where the volume, is read. Or after the
treatment with acetic acid and sulphuric acid, the fat may be left to rise without
any assistance in a Chevalier's cream glass, for instance, but the testing operation
takes then more time and the result is less certain than by using the centrifugal
operation.
In the annexed drawing is shown an apparatus for testing with the aid of
centrifugal force. Fig. 1 represents a plan of the part of the apparatus (laktokrit),
the so called plate into which the different test-vessels to be exposed to centrifugal
action are placed; Fig. 2 is a vertical section of the same along the line 2-2 in
Fig. 1. Fig. 3 is an elevation of one of the test-vessels, with the lower part, or the
box, removed. Fig. 4 is an elevation of the box and Fig. 5 is a cross section along
the line 5-5 in Fig. 3. Fig. 6 is a vertical section of the "Laktokrit " mounted
to be driven by machine power.
The test-vessel consists of a cylindrical silvered metallic box a, into which a
likewise silvered metallic plug. b fits accurately. This plug is turned and bored
hollow from the bottom tapering towards the top into a fine hole communicating

page_text: +
with a fine glass tube c fixed to the plug and either graduated or not graduated.
This glass tube is fixed upon the plug by a nut d, screwed into a socket or holder e,
secured to the plug and surrounding the tube and provided with opposite openings f,
so that the degrees on the tube may be read or the reading may be performed by
means of a graduated plate. The nut is provided with a hole g, so that the plug
and the tube constitute conjointly a vessel or channel, open at both ends. h is a
steel plate provided with a vertical shaft . This plate h has in the upper part
a recess k, in the walls of which holes are made for the test-vessels. The
apparatus represented on the drawing has 12 such holes, but it may of course be
arranged for another number. These holes should preferably be placed radially and
a little inclined downwards towards the circumference.
The tests are carried out in 'the following manner. Into a common test-tube
equal volumes of the milk to be treated and of the above mentioned mixture of
acetic acid and sulphuric acids are introduced: The mixture which has been found
most suitable is composed of 20 volumes of concentrated acetic acid and 1 volume
of concentrated sulphuric acid. The test-tube, closed by a cork perforated by a
small tube of glass, is agitated a little and then heated on a water bath during 5 to
10 minutes, after which it is agitated very vigorously.
The cork is now taken out of the test-tube and the contents are poured into one
of the above described boxes until it is full.
The plug belonging to the box is then pushed in so far as it will go. The little
test-vessel will then be completely filled and the surplus gets away through the
hole in the nut, and thus an accurately measured quantity of fluid is obtained.
The test-vessel is then pushed, the box foremost, into one of the holes in the plate.
In like manner the other specimens to be tested are similarly prepared. The holes
in the plate must previously to the introduction of the test-vessels be filled with
hot water of 50° Cels or more. The hotter the water is the more the heat of the
plate is conserved. Its temperature should be at least 50° Celsius.
All the test-vessels having been introduced, a lid (m Fig. 6) is put on for the
purpose of preventing refrigeration. The apparatus is then put in motion with a
speed of about 6000 revolutions a minute during 3 to 5 minutes. After stopping
the apparatus the test-vessels are taken out and the volume occupied by the fat
column in the glass tube is immediately read. The fat being in a melted state
appears quite transparent and clear, but a determined limit can however be
observed between the fat and the solution of Casëine existing beneath. It occurs
frequently that a little white plug of caseine is visible between the fat and the acid
solution. This seldom exceeds the tenth part of a millimetre in length. If the
.milk is not diluted by water, this plug does not present itself or only traces thereof
are to be seen. The graduations are preferably arranged in such way that 1 of
the number of divisions occupied by the separated fat, just indicates the percentage
of the fat contained in the milk. For instance if 33-5 divisions are read, the milk
*contains 3.35% of fat. The reading can very well be carried to 0.2 division and
thus there occurs an error only of about 0.02%, say an error of 0.5% of the weight
of the butterfat in milk of 4 per cent. As 12 tests can be made by this apparatus
in 10 minutes (the heating of new tests takes place during the testing of the
preceding ones) the great rapidity of 72 tests an hour has been attained, and these
as accurately made as by means of chemical analysis.
°
After use the boxes and plugs are rinsed in hot water and a little such water is
blown through the glass tubes. The boxes and the hollow part of the plugs are
then carefully wiped.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is
1. The method of determining the percentage of fat in milk by treating milk
by the aid of heat with acetic acid and sulphuric acid and then reading the volume
of the separated fat substantially as described.

page_text: 2. The method of determining the percentage of fat by introducing a certain
quantity of milk, treated with acetic acid and sulphuric acid, into a vessel provided
with a fine glass tube open at both ends and by means of centrifugal action causing
the fat together in this tube to be measured, substantially as described.
3. The use of apparatus for determining the percentage of fat in milk, according
to the method indicated in the preceding claim, consisting of a disc, which can be
brought into rapid rotation, provided with a recess in the centre and with out-
wardly inclined holes preferably placed radially, into which the test-vessels are
placed, which vessels consist each of a box with a hollow plug, communicating
with a fine glass tube open at both ends, into which the separated fat is, by means
of centrifugal action, forced substantially as described.
W. LLOYD WISE,
Agent for the Applicant.