BAIRD &TATLOCK: (LONDON) LTD. 



1756 



1756" Balance (Fig. 1755, page 361), packed for export in a zinc-lined case, of which the 



dimensions are Go by 24 by 19 in., and the gross weight about 300 Ibs., or 136 kilos . . 35 



1757 



1758 



1757" Balance for taking Specific Gravities (Westphal's), with riders, plummet thermometer, 

 and forceps, in polished box with directions 



1758 U Balance for taking Specific Gravities, with Mohr's modifications for solids and fluids, 

 with plummet thermometer and set of riders 



DIRECTIONS FOR USE. 



After the instrument is mounted and the beam rests in equilibrium, the glass plummet which contains the 

 thermometer is suspended from the right-hand knife edge of the divided beam and on the double-arm scale counter- 

 poised by the weight included. 



The absolute weight of the plummet including platinum wire amounts to 15 grammes, and the displacement of 

 its volume is equal to 5 grammes of distilled water at 15 C., at which normal temperature these weighings are 

 based ; accordingly the unit rider is 5 grammes, and the smaller ones 0.5, 0.05, and 0.005 gramme. 



To use the balance, the larger rider is put on the same hook with the plummet, and the latter 

 immersed into distilled water until the equilibrium is restored ; in this position the platinum wire twisted around 

 the top of the plummet is always below the surface of the water. If the liquid is lighter than distilled water, i.e., 

 lighter than i. the large rider must be placed somewhere on the divided beam, where it will again produce equili- 

 brium ; but when this occurs at some point between two notches on the beam, this rider must be placed on the 

 notch of lower value of the two between which it rests, and then the next size rider applied to determine the 

 difference. Should the position of this second rider also fall between two notches, the third and eventually the 

 fourth or smallest is brought into use in the same manner as described above with the largest rider. If it happens 

 that two riders come to rest at the same notch, the smaller is suspended from the larger one. In this way the 

 specific gravity of a liquid can be read off down to the fourth decimal place from the divided beam. 



If a liquid heavier than distilled water is tested, the process is the same as described above, with the addition 

 that one of the large riders is always hung from the hook with the plummet, while the other riders cross the beam at 

 the proper points. 



It is obvious that all plummets have the same weight and volume ; broken plummets and lost riders can 

 therefore te replaced without it. being necessary to return the balance. 



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-CROSS STREET HATTOTST GARDETST, E'C 



