i86 



THE ALUMNI JOURNAL. 



etc., according to origin, when solid, 

 paraffine. although this sub-classification 

 is not general or complete. 



Waxes are compounds of a fatty acid 

 with a primary alcohol unusually high 

 in the series, and may be liquid or solid 

 according to temperature, as Sperm Oil, 

 a liquid wax, and Beeswax, a solid. 



It is in all cases essential that the sam- 

 ple of fat, hydrocarbon or wax be clean 

 and clear, free from water, suspended 

 mineral matter and foots before applying 

 any tests. In most cases preliminary 

 drying with gentle heat, and filtration 

 through dry paper or absorbent cotton 

 will effect the desired result ; with the 

 drying oils, however, such treatment 

 would be detrimental, especially if pro- 

 longed, and the dessication might take 

 place in a non-oxidizing atmosphere, 

 as Hydrogen or Carbon Di-Oxide, or 

 filters of water, absorbent material such 

 as neutral Plaster of Paris, Spanish Earth 

 and similar substances may be used 

 without heating. As a rule too little 

 attention is paid to these preliminary 

 details of mechanical purification, and 

 the result is unsatisfactory and unfair. 



The samples should be sufiiciently 

 large, so that the indispensable physical 

 tests may be applied with proper regard 

 to conditions of accuracy, a minimum 

 quantity should be fixed at eight ounces 

 or 250 C.c; in any event sixteen ounces 

 or 500 C.c. will be sufficient. The tests 

 applied should be of two general orders, 

 viz., chemical and physical. 



Of the physical tests that of specific 

 gravity is the most important, provided 

 the proper conditions exist. It must be 

 observed that the heat plays a very im- 

 portant part with these bodies ; hence it 

 is very necessary to make such observa- 

 tions at carefully regulated temperatures, 

 and more certain information may be 

 obtained by making such tests at two or 

 more points, since it has long been the 



custom to fabricate mixtures which will 

 exactly coincide with the density of a pure 

 sample at any given point, say 15.5° 

 Cent., and this falsification would be 

 much more difficult or even impossible 

 if the density was also taken at some 

 elevated temperature, say 99° Cent. 



15-5° 



Cotton Seed Oil. 0.926 



Linseed Oil, o 936 



Peanut Oil, o 920 



Rape Seed Oil, 0.913 



Rosin Oil, 0.925 



Mineral Oil, 0.930 



Menhaden Oil, 0.932 



vSperm Oil, 0.884 



99° 

 0.871 

 0.880 

 0.864 

 0.862 

 0.910 

 0.850 

 0.877 

 0.830 



Butter fat, 0.904 at 40° C. 0.867 at 99° C. 



Butterine, 0.898 " 0.859 



There is some choice in the apparatus 

 to be used in the determination of the 

 density. The oleometer or hydrometer 

 for oils is not sufficiently accurate, and 

 the pyknometer or specific gravity bottle 

 is too slow, besides requiring a balance 

 of great accuracy, and is not applicable 

 at elevated temperatures. 



The specific gravity balance, either ot 

 Mohr or Westphal, fulfils all conditions, 

 is accurate, rapid, and applicable in all 

 cases. The instrument is so well known 

 that no description is necessary — it suf- 

 fices to say that for ordinary tempera- 

 tures the thermometer body, with a range 

 of io°-20° Cent, is used, at all other 

 points the solid glass body serves. 



For high temperatures a deep closed 

 copper water bath is used ; in the top of 

 this bath are three holes — one for a test 

 tube, holding the oil, one for a ther- 

 mometer, and the other for a glass tube 

 for steam exhaust. It is best to provide 

 a small thermometer to place in the test 

 tube of oil. Instead of the copper bath 

 one can be improvised from an ordinary 

 one-quart tin fruit can. Where the sam- 

 ple of oil is very small, application can 

 be made of the so-called Sprengel tube — 

 a U shaped tube of glass one-eighth inch 



