112 



THE POPULAR SCIENCE MONTHLY. 



entitled to have what he pays for, and 

 lie can find out very satisfactorily what 

 it is that he pays for, by the employ- 

 ment of the lactometer. 



Good milk consists of about 88 per 

 cent, water, combined with about 12 per 

 cent, of solid matter dissolved or dif- 

 fused in it, which makes it heavier than 

 water. This increased relative weight 

 is known as its specific gravity, and 

 water being taken as 1000, the specific 

 gravity of milk varies from 1023 to 

 1034. "Without inquiring into the pro- 

 portions of its several solid constituents, 

 the lactometer determines their amount 

 by indicating the specific gravity of the 

 sample tested. The instrument is sim- 

 ply a glass tube closed at the lower end, 

 and properly weighted, with a scale af- 

 fixed, which shows the result when it 

 is floated in a sample of milk. Milks 

 from different cows and at different 

 times vary in richness and poorness, so 

 that it becomes important to fix such a 

 standard that all samples which fall be- 

 low it shall be classed as adulterated, 

 or condemned as unmarketable. The 

 Xew York Board of Health has been 

 engaged for a considerable time, under 

 the intelligent direction of Prof. Chan- 

 dler, in investigating this subject, and, 

 as a result of very extensive observa- 

 tions, they have fixed upon a specific 

 gravity of 1029 as a fair minimum stand- 

 ard for pure milk, so that, " when- 

 ever the gravity falls below this num- 

 ber, the milk may be considered as 

 containing ah excess of water and con- 

 sequently as poor in quality, or adulter- 

 ated." 



The standard adopted is, beyond 

 doubt, sufficiently low. A German 

 chemist tested the milk of 124 cows, 

 and found the maximum specific gravi- 

 ty to be 1034.3, the minimum specific 

 gravity to be 1029.5, and the mean 

 1031.7. Hence the standard of mer- 

 chantable milk adopted by the New 

 York Board of Health is lower than 

 the poorest milk from these 124 cows. 

 It may be remarked that milk of 1034 



will bear an addition of 16.67 per cent, 

 of water to reduce it to 1029. 



This standard has been made legal 

 in New York that is, a dealer selling 

 milk below 1029 is hable to a fine. 

 Whatever may be the result of this 

 policy, a most important step has been 

 taken in fixing a minimum standard, 

 and thus making it possible for milk- 

 buyers, quickly and certainly, by the use 

 of the instrument, to ascertain whether 

 the character of the article they are 

 purchasing is above or below it. We 

 say, then, to every householder inter- 

 ested, get a lactometer. Taglibue, of 69 

 Fulton Street, New York, makes and 

 sells them for $1.25 apiece, with the 

 scale adopted by the New York Board 

 of Health. The instrument is perfectly 

 simple, and will last a hundred years, 

 with care, but it is not a good thing for 

 children to play with. On a card ac- 

 companying it, we read : " Fill the jar 

 with the milk to be tested ; allow it to 

 cool to the temperature of 60 Fahr., 

 then immerse the lactometer and notice 

 the mark on the scale that is level with 

 the surface of the milk, which will 

 show the quality." The standard of 

 pure milk adopted is marked P, and is 

 taken as 100 on the scale. If the lac- 

 tometer stands at that point, the milk 

 is legal. If it sinks below it the milk 

 is too thin, and the point in the scale 

 at which it stands indicates its excess 

 of water. If the mark P stands above 

 the surface, the milk is richer than the 

 standard, and the scale shows its supe- 

 rior quality. Of course, the instrument 

 cannot give an analysis of the milk, and 

 if a milkman reduces a high grade of 

 milk to a somewhat lower standard, by 

 admixture of water, the lactometer 

 cannot show it ; but it will tell exactly 

 the quality of the milk every time, so 

 that the buyer may know how he is 

 being served. The general use of the 

 lactometer could not fail to exert a 

 beneficial influence upon the morals of 

 the milk-trade. 



