SPECIFIC GRAVITY TEST. 211 



This will be sufficient to detect any gross adulteration. The 

 taking of the specific gravity of every churn should be invariably 

 performed, as this indication alone will be sufficient to detect 

 gross adulteration, and it will also give a rough indication of the 

 quality of the milk. For this purpose it is most convenient to 

 employ a thermo-lactometer, or lactometer and thermometer 

 combined in one instrument ; the specific gravity should be 

 corrected to 60° F. by means of Table LXXXI. It is not generally 

 necessary that the chemist should personally take these specific 

 gravities. This may be left to a foreman or other intelligent 

 person who has been trained to this work under the supervision 

 of the chemist. The instructions given to the foreman should 

 be, to pass all milk of a specific gravity lying between certain 

 limits, unless special instructions to the contrary in certain cases 

 are given; these limits may be from I'OSl to 1*031, r0305, or 

 1 ■030, according to circumstances ; but in special cases higher 

 or lower limits may be used. Should the specific gravity of any 

 churn fall outside these limits, the foreman should be instructed 

 to take samples with special care, and send them at once to the 

 laboratory to be further tested ; the milk in this case should be 

 put on one side and not used until the report of the chemist has 

 been received. As it is possible that a dispute, perhaps in a law 

 court, may arise with respect to these special samples, the fore- 

 man should be instructed to seal both the sample, and the churn 

 from which it was taken, so as to prevent any possibility of the 

 milk being tampered with. This preliminary testing has been 

 found to give satisfactory results in the author's experience. In 

 all cases where adulteration of milk before arrival at the dairy 

 has been definitely proved, the specific gravity test revealed 

 that the milk was not of normal quality. As an example of a 

 case in which it was necessary to depart from the usual instruc- 

 tions given to the foreman, the author has found, in the case of 

 the milk received from one particular farm, that the milk had a 

 specific gravity as low as 1'029. As the genuineness of this 

 milk was proved beyond a doubt, the lower limit for the milk 

 derived from this farm was fixed for a certain period at this 

 figure. It will not be necessary to teach the foreman to read 

 the lactometer closer than half a degree, as this is an approxi- 

 mation quite sufficient in practice. 



Undoubtedly, the most perfect control over the milk would 

 •consist in the analysis of the milk in every churn before it is 

 used, and the rejection of those churns in which the milk does 

 not come up to the standard of purity adopted. This is, how- 

 ever, hardly practicable in a large dairy, as the mUk must be 

 dealt with and sent out as soon as it arrives, and the time for 

 analysis is short. It has been found that the time required for 



