1 56 CHE MIS TR Y FOR A GRICUL TURAL STUDENTS 



CD 



00=^ 



^ 



)^j^ 



J^ 



Fig. 50. 



of copper wire, with the end bent into a ring 

 of such a size that it will easily move up and 

 down in the vessel of water without touching 

 the thermometer and tube. Having arranged 

 the apparatus, as figured, slowly heat the 

 water, with constant stirring, until the frag- 

 ment of fat is just melted. Note the 

 melting point. Now allow to cool, still 

 constantly stirring, and note the solidifying 

 point. Repeat the alternate heating and 

 cooling until the exact melting point and 

 solidifying point are ascertained with cer- 

 tainty. Then determine the melting point 

 of the other fat. 



The melting points of the fats of special 

 importance and their specific gravities (deter- 

 mined at 66° C. and compared with water at 



the same temperature) are as follows : — 



Fat. 



Melting Point. 



Butyrm, C3H5.3C4H7O2 

 Myristin, C3H^.3Ci4H2702 



Palmitin, 



^3-'-^5'3^16^31 



Olein, 



^3^5' 3^18^33^2 



Stearin, C3H5.3C18H35O2 



? 



55' 

 62° 



72= 



C. 

 C. 



c. 

 c. 



Specific Gravity. 

 1. 021 



? 

 0.900 

 0.900 

 0.892 



It will have been noticed that the boiling point or melting point of the 

 hydrocarbons and alcohols of any homologous series rise as the molecular 

 weight of the compound increases. This is obviously the case also with 

 the fats, but with one apparent exception, viz. olein. If, however, the 

 formulae are examined, it will be found that whereas all the other fats are 

 referable to the general formula, C3H5.3CnH2n-i02, and therefore belong 

 to the same series, olein is not referable to this formula ; so that the apparent 

 discrepancy is understood. As a matter of fact, while butyric, myristic, 

 palmitic, and stearic acids are derived from the paraffin series of hydro- 

 carbons, oleic acid is derived from the olefine series. The same variation 

 in the physical properties, with the increase in the molecular weights, is 

 observed in the acids themselves. While formic, acetic, and butyric acids 



