y 
How Can I Determine Total Milk Solids? 
Give Us a Simple and Reliable Test 
Can you tell me if there is any simple way to test 
milk for the per cent of solids? I have a Babcock tester 
which we use regularly. In this State they are getting 
most strict as to the solids. They require 12 per cent, 
and I know of one case where they excluded from the 
market milk that tested very slightly below the standard 
in solids, although it was well above the standard of 
8.35 per cent fat. joriN g. ei.lis. 
Massachusetts. 
OU can secure a lacto-thermometer, and by using 
it in connection with the Babcock test, can de¬ 
termine accurately enough for practical purposes the 
per cent of solids in your milk. A complete treatise 
on the lactometer and its use follows: 
PRINCIPLE UPON WHICH IT OPERATES.— 
The lactometer works on the principle that a body 
floating in a liquid displaces an amount of the liquid 
milk, and therefore the weight of a given volume of 
milk to which some water has been added is de¬ 
creased. 
(4) The addition of skiiu-milk or the removal of 
cream. Skim-milk is heavier than milk, hence the 
addition of skim-milk to milk, or the removal of 
some of the cream, increases the weight of a given 
volume of milk. 
OPERATION OF THE TEST.—The sample must 
be representative and thoroughly mixed, as for the 
Babcock test. The temperature of the milk must be 
between 50° and 70° F. A glass cylinder is filled 
with the milk and set in some receptacle, such as a 
sink or a pan. The lactometer is then slowly lowered 
into if. In a few minutes the lactometer becomes sta- 
than at GO 0 F. and the lactometer will not sink as 
deep in displacing its own weight, and the reading 
will be too high. Therefore, subtract the .1 when 
temperature is below 60° F. 
Calculation of the specific gravity of milk.—The 
rule is to divide the lactometer reading by 1.000 and 
add 1 to the result. Thus if the lactometer reading 
at 00° F. is 32. 32 -4- 1.000 = .032. + 1 = 1.032 spe¬ 
cific gravity. The specific gravity always equals the 
lactometer reading with 1.0 in front of it. 
Calculation of the per cent S. X. F. and T. X. in 
milk: To find the solids in milk both lactometer and 
Babcock tests must be made and then this formula 
used: % L + (20 x % fat) = % X. N. F. L. is the 
correct lactometer reading. For example, if the 
equal to the weight of the floating body. In other 
words, if a glass cylinder is filled level full of milk 
and the lactometer floated into it. the weight of the 
milk that runs over is equal to the weight of the lac¬ 
tometer. 
DESCRIPTION OF THE INSTRUMENT.—At the 
bottom is a large bulb filled with shot or mercury to 
keep the lactometer in an upright position when 
floating. Just above this is the bulb of a thermom¬ 
eter, the paper scale for which is located at the top 
of the instrument. Above this bulb is a large air 
chamber for floating the lactometer, and just above 
this air chamber is a paper lactometer scale reading 
in lactometer degrees from 15 at the top down to 40. 
FACTORS AFFECTING WEIGHT OF MILK.— 
(1) Temperature. Ileat causes milk to expand, and 
hence a given volume to weigh less, while cold causes 
milk to contract and a given volume to weigh more. 
This is plainly shown on the farm in cooling milk. 
A can full of warm milk put into the cooling tank 
at night is no longer full in the morning, and has to 
be “topped out" before shipping. 
(21 The per cent of total solids normally present 
in milk. As the per cent of fat increases in milk, the 
per cent of solids not fat also increases, so that a 
quart of 5 per cent milk, for example, will weigh 
slightly more than a quart of 3 per cent milk. 
(2) Addition of water. Water is lighter than 
tionary and the lactometer scale is read at the point 
where the surface of the milk cuts it. This reading is 
recorded and the temperature noted and recorded. 
Since the temperature affects the weight of a given 
volume of milk and hence the lactometer reading, 
obviously the reading must be taken at some definite 
temperature, or readings corrected to that tempera¬ 
ture. The lactometer gives a correct reading directly 
only when the milk is at G0° F. If the milk is be¬ 
tween 50° and 70° F. a correction can be used to 
give a corrected reading. The correction is .1 of a 
lactometer degree added to the lactometer reading 
for each degree of temperature above 60° F. and sub¬ 
tract a .1 for each degree below 60° F. Thus, if a 
lactometer reads 30 at 68° F.. the correct reading is 
30.8, and if 20.5 at 53° F.. the correct reading is 2S.S. 
If one tries to memorize this rule it leads to con¬ 
fusion. Reason it out as follows: (1) The lactome¬ 
ter works on the principle of displacing its own 
weight of milk when floated in it: (21 the lac¬ 
tometer scale reads just opposite from a thermom¬ 
eter scale, namely, down; (3) if milk is above GO 0 F. 
the weight of a given volume is less than at (10° F. 
Hence the lactometer must sink deeper into the milk 
to displace its own weight, and the reading will be 
too low. Therefore, add the .1 if temperature is 
above (50° F. On the other hand, if temperature is 
below (10° F„ a given volume of milk weighs more 
lactometer reading is 32.5 at 55° F. and the fat test 
3.0%: 
Correct L = 32 
Vt of 32 = S 
20 X .030 = ,7S 
2 4- .78 = S.78 % S. N. F. 
% T. S. = S. X. F. 4- fat. therefore % T. S. = 8.7S 
+ 3.0 = 12.08. 
STATE AND FEDERAL STANDARDS.—The rea¬ 
son why we need to know how to find the per cent of 
solids not fat and total solids in milk is because 
practically evely State in the Union and the Federal 
Government have standards defining lawful milk. 
The standards are stated in terms of per cent fat, 
per cent S. N. F. and per cent T. S. For example, 
to sell milk in Massachusetts, it must contain 3.35% 
fat. 8.05% S. N. F. and 12% T. S. The Federal re¬ 
quirements are 3.25% fat, 8.5%'S. N. F. and 11.75% 
T. S. The various State standards differ somewhat, 
but more of them have the Federal standard than 
any other. The Federal standard applies in inter¬ 
state traffic. That is. if a farmer from New York, 
for example, with 3% fat standard, wants to ship 
milk into Massachusetts, it must test at least up to 
the Federal requirement, 3.25%. plus 1% to con¬ 
form to the Massachusetts requirement but he 
could sell 3% milk in New York without being liable 
to punishment. Most States have dairy and food 
commissioners, and the enforcement of these laws is 
