ELECTRICAL RESISTANCE UNDER PRESSURE. 145 



pressure coefficient of the liquid at 62.5° is O.Os'id, and at 1G5° this 

 has dropped to O.O3I7. 



Liquid gaUium shows a rather large decrease of the instantaneous 

 pressure coefficient with rising pressure. At 30° the values of the 

 coefficient at 0, 6000, and 12000 kg. respectively are O.O564O, O.O5535, 

 and O.O549O. x\t 100° the corresponding values are 634, 541, and 491. 

 The effect of temperature on the pressure coefficient is therefore 

 relatively slight; at the lower pressures the coefficient decreases with 

 rising temperature, and at the higher pressures it decreases. The 

 mean temperature coefficient of resistance between 30° and 100° 

 changes relatively little, being 0.000S15, 829, and 808 at 0, 6000, and 

 12000 kg. respectively. Compared with sodium and potassium the 

 changes of all the coefficients of gallium are relatively small. It is 

 to be remarked also that the pressure coefficient of gallium is of the 

 same order of magnitude as that of many solid metals ; we have come 

 to expect relatively slight variations of the coefficients of those sub- 

 stances with small coefficients. 



Liquid bismuth was measured over only part of its region of stability, 

 so that again complete results are not at hand. At 275° the instan- 

 taneous pressure coefficient drops from O.O4I23 at kg. to 0.0594 at 

 6000 kg., and at 240° the coefficient is O.O592 at 6000 kg., and O.O58O 

 at 12000. The temperature coefficient of resistance at 275° drops 

 from 0.00047 at kg. to 0.000453 at 6000 kg. Liquid bismuth is 

 therefore entirely normal in all respects, that is, a falling pressure 

 coefficient with rising pressure and falling temperature, and a falling 

 temperature coefficient with rising pressure. This complete normal- 

 ity is in spite of the fact that solid bismuth is abnormal in having a 

 positive pressure coefficient. The presumption is therefore very 

 strong that the abnormahty of the solid is mainly due to the crystal- 

 line structure. It is known of course that bismuth crystallizes in the 

 hexagonal system which is not normal, nearly all the elements being 

 cubic. 



Summarizing, except for potassium, the behavior of all these liquid 

 metals is of the same type; the pressure coefficient decreases with 

 rising pressure and increases with rising temperature, and the tem- 

 perature coefficient decreases with rising pressure. 



Abnormal Liquids. Only one abnormal liquid, that is, a liquid 

 with a positive pressure coefficient of resistance, is known, liquid 

 lithium. For this the relation between pressure and resistance was 

 linear within the limits of error and the coefficient was independent of 

 temperature between 200° and 240°. A linear relation between 



