52 FOODS AND FOOD ADULTERANTS. 



;3rd and adulterated butters are still somewhat opalescent. From this 

 it is seen that the data obtained by the old method of determining the 

 temperature of transparency would differ somewhat from those obtained 

 by the proposed procedure. Since the age of the disk has a great deal 

 to do with its melting point, I suggest that all determinations be made 

 within fifteen minutes to two hours from the making of the disks. 



The method can also be extended to such bodies as paraffine and 

 bees- wax. The melting point of a paraffiue was found to be 



An interesting phenomenon was observed in determining the melting 

 point of the paraffiuc, which may be made to show, in a lecture experi- 

 ment, the change of volume which bodies sometimes undergo in passing 

 from a solid to a liquid state. The same mixture of water and alcohol 

 used in the examination of fats, allowed the disk of paraffine to sink to 

 about the same point as the disk of fat. When the temperature rose, 

 however, to within one or two degrees of the melting point, there was a 

 sudden increase in volume. The pellet of paraffine rapidly rose to the 

 top of the tube. To avoid this and keep the globule within the liquid 1 

 made a mixture of water-alcohol aud absolute alcohol. With this 

 arrangement the rise of the paraffiue was arrested in the upper third 

 of the tube occupied by the absolute alcohol, where its assumption of 

 the spheroidal state could be readily observed. On placing the tube in 

 a cooling bath the globule of paraffine rapidly sinks as it solidifies- 

 The disks of paraffine aud bees- wax are quite irregular, but nevertheless 

 suitable for the process. The melting point of the one sample of bees- 

 wax examined was found to be C4.2 0. 



VISCOSITY. 



The speed with which at identical temperatures an d pressures dif- 

 ferent oils flow through an orifice may be used to dintinguish them 

 from each other. For a description of the methods used in viscosime- 

 try 1 refer to Allen's Com. Organic Analysis. 1 An ingenious aud useful 

 apparatus for viscosimetry has been invented by Babcock. 2 



Babcock has applied his apparatus to the investigation of the viscos 

 ity of butter soaps with promising results. 3 



1 Vol. 2, 2d cd., pp. 104 et scq. 



2 Fifth Ann. Kept. Bd. Control N. Y. Exp. S.ta., pp. 316 ct acq. 



3 Ibid., pp. 338etscq. 



