EXAMINATION OF DAIRY PRODUCTS. 51 



extreme difficulty. During the last few years considerable progress 

 has been made in the attempt to renovate butter in such a way that it 

 will appear like fresh butter in all respects. A study must be made 

 of these methods if we would obtain reliable results. 



The " spoon " test has been suggested as a household test, and is 

 commonly used by analytical chemists for distinguishing fresh butter 

 from renovated butter and olepmargarin. A lump of butter two or 

 three times the size of a pea is placed in a large spoon and heated over 

 an alcohol or Bunsen burner. If more convenient, the spoon may be 

 held above the chimney of an ordinary kerosene lamp, or it may even 

 be held over an ordinary illuminating gas burner. If the sample in 

 question be fresh butter it will boil quietly, with the evolution of 

 many small bubbles throughout the mass which produce a large amount 

 of foam. Oleomargarin and process butter, on the other hand, sput- 

 ter and crackle, making a noise similar to that heard when a green stick 

 is placed in a fire. Another point of distinction is noted if a small por- 

 tion of the sample be placed in a small bottle and set in a vessel of 

 water sufficiently warm to melt the butter. The sample is kept melted 

 from half an hour to an hour, when it is examined. If renovated but- 

 ter or oleomargarin, the fat will be turbid, while if genuine fresh but- 

 ter the fat will almost certainly be entirely clear. 



To manipulate what is known as the "Waterhouse" or "milk" test, 

 about 2 ounces of sweet milk are placed in a wide-mouthed bottle, which 

 is set in a vessel of boiling water. When the milk is thoroughly 

 heated, a teaspoonful of butter is added, and the mixture stirred with 

 a splinter of wood until the fat is melted. The bottle is then placed in 

 a dish of ice water and the stirring continued until the fat solidifies. 

 Now, if the sample be butter, either fresh or renovated, it will be solid- 

 ified in a granular condition and distributed through the milk in small 

 particles. If, on the other hand, the sample consist of oleomargarin it 

 solidifies practically in one piece and may be lifted by the stirrer from 

 the milk. 



By these two tests, the first of which distinguishes fresh butter from 

 process or renovated-butter and oleomargarin, and the second of which 

 distinguishes oleomargarin from either fresh butter or renovated but- 

 ter, the nature of the sample under examination ma}^ be determined. 



The oldest and simplest method of adulterating milk is by dilution 

 with water. This destroys the natural yellowish-white color and pro- 

 duces a bluish tint, which is sometimes corrected by the addition of 

 a small amount of coloring matter. 



Another form of adulteration is the removal of the cream and the 

 sale as whole milk of skimmed or partially skimmed milk. Again, 



