HYDROMETER SCALES. 383 



Strontium Sr 87'6 Tungsten W 184 



Sulphur S 32-06 Uranium U 239-5 



Tantalum Ta 183 Vanadium V 51-2 



Tellurium Te 127'6 Ytterbium Yb 173 



Thallium Tl 204-1 Yttrium Y 89 



Thorium Th 232-5 Zinc Zn 65-4 



Tin Sn 118-5 Zirconium Zr 90'7 



Titanium Ti 48 -1 



In addition, Krypton, 81 '8, Neon, 20, 'Xenon, 128, Gado- 

 linium, 156, and Thulium, 171, are to be added to the table. 



THE CONNECTION BETWEEN VARIOUS HYDROMETER SCALES 

 AND THE TRUE SPECIFIC GRAVITIES OF LIQUIDS. 



In England, for technical purposes, Twaddle's hydrometer is 

 often employed. This applies to liquids heavier than water. 



The relation between degrees Twaddle and true specific 

 gravity is such that T. corresponds to a specific gravity of 

 1, while the general formula is 



l+ioo 



d = 10Q , or n = 200 (d-l) 



where d = true specific gravity 

 and n = degrees Twaddle. 



Twaddle's hydrometers are, perhaps, based upon a more 

 rational system than most of the other hydrometers. The 

 determinations should be made at 15-5. 



In France, Baume's hydrometers are in general use. For 

 liquids heavier than water a hydrometer which sinks to in 

 pure water and to 10 in a 10 % solution of common salt, both 

 at 17 > 5 C., is employed and a uniform scale engraved on the 

 stem." 



For liquids lighter than water, an instrument which sinks to 

 the zero point in a solution of one part of common salt in nine 

 parts of water, and to a point marked 10 iu pure water, is 

 constructed and the graduation extended as before. 



* Most of the modem Banni^'s instruments are so constructed that in water they 

 read at 15 C. and in sulphuric acid of sp. gr. 1'8427 they read 66. 



