SPECIFIC GRAVITY AND DISPLACEMENT OF SOME SALINE SOLUTIONS. 49 



mark, and at the standard temperature, is obtained. In that method the mean values 

 of the added weights and the corresponding scale readings are utilised to obtain 

 one value of the specific gravity of the solution. The conditions of the method are 

 that exactly the same volume of the hydrometer shall be immersed in the solution 

 and the distilled water, the temperature of both being the same, and the total weight 

 required to cause the instrument to float at 50 mm. in the saline solution divided 

 by the total weight required to float it at the 50-mm. mark in distilled water gives 

 the specific gravity of the solution. 



In an experiment the hydrometer is loaded with nine successive weights in- 

 creasing by O'l gram in each step, and the reading of the stem is observed after each 

 addition. It is evident that if we take the first of the readings and find the weight 

 that would have to be added to the hydrometer when it was floating at the same 

 level in distilled water, the ratio of the two total weights would give a value for 

 the specific gravity of the solution. In a similar way we might use the second 

 scale reading as the basis for another computation of the specific gravity ; and, in 

 general, each of the nine values of the scale readings, obtained by the addition of 

 successive increments of O'l gram to the stem of the hydrometer, furnishes a separate 

 basis for determining the specific gravity. Proceeding in this manner, the accompany- 

 ing table has been compiled. 



Table giving Specific Gravity o/" 1/32 i?6C/+ 1000 grms. H^O at 19 '5° C. 



(a) Time : 2.00 p.m. 



tv. 



t. 



dwi. 



W. 



R. 



Wh,o. 



S. 



0-91 



19-5000 





181-821300 



5^9 



181-314344 



1-002796 



1-01 



-4975 



-000065 



•921235 



170 



•413622 



798 



1-11 



•4950 



130 



182-021170 



28-2 



•514932 



789 



1-21 



•4925 



195 



•121105 



39-3 



•613497 



795 



1-31 



•4900 



260 



•221040 



50-5 



•715553 



781 



1-41 



•4875 



325 



•320975 



61-5 



-814891 



783 



1-51 



•4850 



390 



•420910 



72-3 



-911848 



798 



1-61 



•4825 



455 



•520845 



83^5 



182-010671 



800 



1-71 



•4800 



520 



■620780 



94-9 



•112-200 

 Mean 



792 

 r002793 



(b) Time : 2.31 p.m. 



IV. 



t. 



dWf. 



W. 



R. 



W„,o. 



S. 



0-91 



19-5000 





181-821300 



6^5 



181-319701 



1-002766 



roi 



•5062 



-000161 



•921461 



179 



•421691 



54 



111 



•5124 



322 



182^021622 



29-0 



-522019 



52 



1^21 



•5186 



484 



•121783 



40^0 



•619795 



64 



1-31 



•5248 



645 



-221944 



51-1 



•721003 



61 



1-41 



-5310 



806 



•322105 



62-1 



•8-20278 



60 



1-51 



•5372 



967 



•422266 



73-1 



-918880 



67 



1-61 



-5434 



-001128 



•522427 



84-2 



182-016885 



77 



1-71 



•5500 



1300 



•622588 



95-5 



-117518 

 Mean 



73 

 1-002764 



TRANS. ROY. SOC. EDIN., VOL. XLIX., PART I. (NO. 1). 



