SPECIFIC GRAVITY AND DISPLACEMENT OF SOME SALINE SOLUTIONS. 



R. 



immersed in distilled water and accessory weights are added until it floats almost totally 

 immersed in the water, the sum of the accessory weights, the weight of the glass, and 

 that of the lead give the weight of the water displaced, and from this the external 

 volume, or the displacement, of the instrument is obtained. The volume of the air 

 inside the hydrometer is then given by the difference between the external volume of 

 the instrument and the sum of the volumes of the glass and lead. Full details of the 

 experimental work required in order to obtain the exact weight of the hydrometer 

 under particular conditions are given. 



SECTION XIL 

 NuMEBiCAL Details illustrating the Use of the Open Hydrometer. 



85. Details are furnished relating to the experimental determination of the weight of the 165 



liquid displaced by the instrument designated Hydrometer A. 



86. Scheme for logging the observations made with the hydrometer in the experimental 167 



liquid at the selected standard temperature, T. A table gives numerical examples using 

 (a) distilled water, and (b) a 7 gram-molecule solution of rubidium chloride. 



87. Correction for the buoyancy of the non-immersed portion of the stem. As in the case of 169 



the closed hydrometer, this is practically inappreciable. 



88. The degree of accuracy attainable l)y the use of the open hydrometer is illustrated by the 169 



results of five series of observations, each series consisting of eleven independent 

 observations, made in a solution of calcium chloride containing 6*3 gram-molecules of 

 CaCig in 1000 grams of water. Of the five series, three were made vvith hydrometer A 

 and two with hydrometer B. The values of the mean specific gravities, S, furnished 

 by each series and its probable error ( ± r^), expressed in units of the sixth decimal place, 

 are collected in a table. 



89. Precautions to be taken in order to secure trustworthy results. My practice in the 171 



CJiallenger was, when I began hydrometric observations, to lock the door, and I still 

 adhere to this practice. Attention is called to the effect of the low specific heat of 

 concentrated solutions, such as 6 3 CaClg, in increasing the thermal nimhleness of the 

 solution. 



.90. Table of specific gravities calculated from single observations made with hydrometers A 172 



and B when floating in a solution of calcium chloride containing 6"3 gram-molecules of 

 CaClg in 1000 grams of water. This table includes the individual observations the 

 means of which were given in § 88. 



SECTION xm. 



On the Specipic Gravity and Displacement of Solutions op Salts of the Ennead MR which 



HAVE nearly the SAME MoLECULAR WEIGHT AND MAY BE LOOKED ON AS " ISOMERIC." 



91. These salts are RbCl, KBr,K 51+1. 172 



92. A table gives the results of specific gravity determinations made upon the solutions of 173 



these salts at 19 "5' C. 



93. The solubility of each of the above salts was determined. 174- 

 TRANS. ROY. SOC. EDIN., VOL. XLIX., PART I. (NO. 1). 2 



