COLD TEST. 



There seem to be several objections to the method for the cold test 

 as given by the Prussian State Railway Direction, some of which are 

 based on its complications, although it seems that the method might 

 be readily modified so as to be extremely practical and rapid. The 

 chief objection, however, is the fact that the oil is not stirred in anyway 

 while cooling, and it is a well-known fact that oils can be cooled to a 

 considerable degree below their crystallizing points if kept perfectly 

 quiet, while lubricating oils in actual use are in motion. The chief 

 advantage of the method is that it eliminates the personal equation as 

 to whether the oil flows or not. It seems to be the consensus of opin- 

 ion, however, that a simpler method, such as that used by the Penn- 

 sylvania Railroad and by the United States Navy Department, with 

 perhaps some slight modification in the manner of carrying out the test, 

 would satisfy every requirement of accuracy and speed. 



A number of valuable suggestions have been brought out by corre- 

 spondence with the various chemists. W. H. Low, of the Cudahy 

 Packing Company, says: "The trouble with all flow tests is that the 

 solidified oil may move as a piston, owing to the sides of the container 

 being warmer than the body of the oil." This trouble is overcome to a 

 certain extent by the scheme suggested by J. P. Millwood, of the Brook- 

 lyn Navy- Yard, of insulating the bottle with a holder of asbestos pipe 

 covering. It seems to the referee, however, that even this insulating of 

 the bottle might be insufficient in many cases, and that perhaps warm- 

 ing up in a bath not far from the flowing temperature would give better 

 results. It seems also that the oil should be stirred as it is cooled, in 

 order to give it a more uniform texture and make the melting more 

 even. Oil is a mixture of fats of various crystallizing points, and only 

 by continued stirring while cooling can the various constituents be uni- 

 formly mixed. 



The need of a special thermometer which can be read without remov- 

 ing from the bottle was noted by Robert Job, of the Philadelphia and 

 Reading Railroad, and by J. P. Millwood, of the Brooklyn Navy- Yard. 

 The latter thus describes the thermometer used by him: "The special 

 thermometers used are graduated in degrees from to 100 F and are 

 18 inches long, with the zero point about 7 inches above the bulb, 

 which brings it outside the bottle." 



The importance of the element of time in the test has been empha- 

 sized by several chemists, and it is on this point that we find the greatest 

 divergence in practice. The experience of many indicates that definite 

 conditions as regards time will have to be made. It is possible, how- 

 ever, that in a method requiring continued stirring the time factor would 

 not be so important. 



Thomas Gladding suggests making the cold test by placing the oil in 



