LACTO METER. is the name of an instrument, invent ed by Dicas, mathematical instrument maker in Liver pool, for ascertaining the different qualities of milk, or the richness of milk, from its specific gravity, compared with water, by its degree of warmth taken with a standard ther mometer. As we have never seen the instrument, we have taken the knowing description of it from the Agricultural Survey of Lancashire.
It is constructed with ten divisions upon the stem, simi lar to the patent brewing hydrometer, and with eight weights, which are to be applied only one at a time upon the top, to obtain the weight of milk ; an ivory sliding-rule accompanies the instrument, upon the middle or sliding part of which is laid down the lactometer weight of the milk, going from 0 to 80 ; and opposite thereto are placed the various strengths of the milk, from water to 160; 100 having previously been fixed upon, from a number of ex periments, as the standard of good new milk, and each of the other numbers bearing a proportionate reference there to. At one end of the sliding rule, the degrees of heat, from 40 to 100, are placed, with a star opposite, as an index to fix the slide to the temperature of the milk the whole being graduated to spew the exact strength of the milk, as it would appear in the temperature of 55• of heat, although tried in any inferior or superior temperature between 40• and 100° : thus the great inconvenience which would at tend bringing the milk at all times to one temperature is avoided, and a simple mechanical method of allowing for the contraction and expansion substituted. And as skimm ed milk, being divested of the particles of butter which ex isted before skimming, appears to have a less degree of affinity with that than the new milk has, one side of the ivory sliding-rule is adapted to skimmed, and the other to new milk.
General Rule.—First, find the temperature of the milk with the thermometer, and fix the sliding-rule so that the star shall be facing the degree of heat the mercury rises or falls to ; then put in the lactometer, and try which of the weights, applied to the top, will sink it to some one divi sion upon the stem ; add the number of the weight upon the top, and that of the division together, and opposite the same, formed upon the side, will be shewn the strength of the milk.
Examples of New Milk —If, in the temperature of 72°, the lactometer with the weight 40 sinks to nine upon the stem, fix the slide so that the star shall be facing 72°; then opposite 49 will be found 100, the strength of the milk. Again, if in 60° the lactometer with 50 on the top sinks to 6 upon the stem, the slide being fixed for new milk, so that the star shall be at 60 degrees of heat, then facing 56 will be found 110, the strength of this milk in proportion towards the other, provided it is equally replete with cream. To discover which, it becomes requisite these two samples should stand a certain time, that the cream may rise, which, being taken off, they are to be tried with the lactometer again: and as the cream is evidently the lighter part, the milk will appear by the lactometer denser or better in quality than before. Suppose the milk in the first exam ple to be 57 by the lactometer in 60° of heat, then the strength by the skimmed-milk side of the rule will he 112. And admit the second example of new milk to be 58 in se when skimmed, the strength would be 116.
From which it appears, that No. 1. has produced a lar ger quantity of cream than No. 2. and consequently may be deemed the better milk. Some instances have occurred where the strength of new milk has only been about 80, and when skimmed near 100. Thus it may, without the least impropriety, be called a milk much better adapted for making butter than cheese ; the serum or whey in general being near the same density.
The instances in which the lactometer may be useful are, according to the same writer, in discovering what breeds of cattle are most advantageous ; what food in the winter season, whether carrots, turnips. potatoes. &c. are best ; what the effects of different pastures may be ; how far particular farms arc best adapted to making butter and cheese ; how far the inconvenience of large cheeses in some dairies being too rich to stand may be prevented, by discovering when this redundancy of richness exists in the milk ; and in fixing a standard for the sale of this useful article of life.