BUTYRO-EEFEACTOMETER. 351 



Margarine has a value of about 52° at 35°, coco-nut oil of 

 41°, and cotton-seed oil of 61°. 



The remarks made upon the oleo-refractometer apply equally 

 well to the butyro-refractometer, except that the actual values 

 are not identical. 



The author's experience confirms that of Mansfeld, and shows 

 that, while Muter's relation is, broadly speaking, correct, there 

 are differences so large between the refractive index found and 

 that calculated on the assumption that this property follows the 

 Reichert value, that the rule cannot be depended upon. The 

 refractive index is a property which is much more nearly related 

 to the iodine absorption, or, in other words, to the unsaturated 

 carbon atoms. 



Though a very convenient test, it has but little value alone, 

 unless the value is below the average, 46° at 35° C, but in the 

 presence of coco-nut oil and margarine an adulterated butter 

 may give a normal figure. When a butter is adulterated with 

 vegetable oils — e.g., cotton seed — its indications are of some 

 value. It is also useful in detecting coco-nut oil, but its value 

 is chiefly corroborative. 



A standard fluid [normal fliissigkeit) is supplied with the instru- 

 ment, and the readings of the scale should be checked from 

 time to time by its use. The point at which the dividiiii; line 

 should lie at 35° C. is marked in the instrument, and tlic scale 

 should be brought to this point by means of a key just above the 

 prisms. 



Viscosity. — Killing proposes to take the viscosity of butter 

 fat as a test by running it out of a pipette, marked above and 

 below the bulb, and records the time taken for the melted fat to 

 flow from one mark to another. The instrument must be gradu- 

 ated with butters and other fats of known purity. 



He gives the following average times of flow : — 



Butter, . 3 minutes +3^ seconds. 



MargariUL-, . 4 ,, 10 



Lard, . 1 ,, 2S „ 



Beef fat, . . . -1 „ 33 „ 



Weuder uses an apparatus called a fluidimeter. This consists 

 of a U-shaped capillary tube having at one end an enlargement 

 holding 10 c.c, and at the other an enlargement holding 2 c.c. ; 

 the larger bulb is placed higher than the smaller ; liquid, there- 

 fore, flows from it. A solution of the fat in chloroform is used ; 

 the upper bulb is filled with this, the solution allowed to flow 

 into the lower bulb, and the time noted which it takes to pass 

 from the lower mark to the upper one on the smaller bxilb. The 

 time taken for chloroform to flow is also noted, and this is taken 

 as 100. 



