K. DOMESTIC AND HOUSEHOLD ECONOMY. 503 



ly, by abstracting from them the whole or a part of their 

 moisture by the assistance of some salt, which, remaining in 

 part in their tissues, prevents the atmospheric air from en- 

 tering, and preserves them from the attack of insects. The 

 salt which best accomplishes this object, under the threefold 

 effect of rapidity of action, the perfection of the products ob- 

 tained, and their salubrity, he considers to be the acetate of 

 soda. 3 i?, 3Iay 22, 1873, 156. 



DETEEMINIXG THE PUEITY OF BUTTER. 



An important paper w^as recently published in the Liver- 

 pool and Manchester Medical and Surgical Re^oorts, by Dr. J. 

 Campbell Brown, in reference to the most practicable meth- 

 ods of determiningj the extent and character of the adultera- 

 tions of butter. The various processes are i^rincipally chem- 

 ical and spectroscopical, but are, to a considerable extent, 

 sufficiently practical to form the basis of very definite exper- 

 iment. As a i^reliminary, an ounce of the sample of butter 

 to be examined is placed in a test tube seven eighths of an 

 inch in diameter, and melted by the immersion of the tube in 

 hot water. A thermometer with a pear-shaped bulb is then 

 to be introduced, so that the bulb shall be in the middle of 

 the fat, about an inch below the surface ; after which the 

 whole is allowed to cool spontaneously. If the quantity of 

 water in the butter be large, it will collect in the tube be- 

 low the fat. Caseine will also collect in the lower part of 

 the tube. The temperature is to be carefully noted when 

 solidification commences, and when it is complete. 



If the butter is pure, the thermometer is obscured between 

 74 and 68, and it is solid at 61. An addition of beef drip- 

 ping causes the thermometer to obscure at 79, and to be- 

 come solid at 72. Mutton obscures the thermometer at 

 about 85, and it is solid at 84. Lard obscures the ther- 

 mometer at 84, and is solid at from 79 to 70, but often re- 

 mains as soft as butter at a much lower temperature. Mixt- 

 ures solidify at intermediate temperatures. 



If pure butter be examined by the microscope, with a one- 

 fourth or one-fifth inch object-glass, nothing will be seen ex- 

 cepting the characteristic globules, the granular masses of 

 curd, and the cubical crystals of salt in the butter. The 

 hard fats are present in the globules, in a state of solution, 



