48 



MR J. Y. BUCHANAN ON THE 



tion, 188-2521 +0-0840= 188-3361 grams (col. k). Dividing this number by 181*7893, 

 we obtain for the specific gravity of the solution, amended for the weight of meniscus, 



^h- 



188-3361 

 181-7893 



= 1-036013 (col. Z). 



The difference between the two specific gravities is 1-8 in the fifth place. This 

 difference is higher than the average. In the case of the nearly saturated solution of 

 NaCl, sp. gr. = ri932, the difference is only 1 in the fifth place. In the corresponding 

 solutions of KCl the difference in the dilute solution is 1, and in the concentrated 

 solution 2, in the fifth place. In the case of CaClg both solutions are of considerable 

 concentration ; the difference in the more concentrated is 2, and in the less concentrated 

 r7, in the fifth place. In the case of MgClg the difference in the dilute solution is 1, 

 and in the concentrated solution 0-4, in the fifth place. It is therefore evident that 

 the specific gravity of solutions determined by the hydrometric method is not affected 

 by an error due to the influence of the meniscus which calls for correction. 



The specific gravity of the less concentrated NaCl solution is 1'036, that of average 

 oceanic sea-water is not greater than r027 ; therefore the influence of the meniscus in 

 sea-water of highest concentration would be not greater than 1 in the fifth place. 

 Tn all my hydrometric ivork on sea-water the infiuence of the meniscus has been dis- 

 regarded, because I recognised from the beginning that the ratio of the iveights of the 

 meniscus must be the same as that of the masses of the liquids displaced by the same 

 im,mersed portion of the hydrometer, unless their volumes differed considerably, and of 

 this there was no evidence. 



a. 



h. 



e. 



d. 



il-0822c^. 



l-0822e. 



g- 



h. 



hxb. 



i. 



h+f. 

 J- 



i+g. 



k/j. 

 I. 



l-b. 

 m. 



Salt 

 dis- 

 solved. 



Without 

 Meniscus. 



Temp. 

 °C. 



20 

 20 

 15 

 15 

 15 

 15 

 19 

 19 



Surface- , height in 

 tension, M,-n;„^o„,c «f 



Without Meniscus. 



With Meniscus. 



With 

 Meniscus. 



Difference. 



Specific 

 Giavityof 

 Solution. 



dynes 

 per cm. 



Meniscus. 



Weight of 

 Hydrometer in 



Weight of 

 Hydrometer in 



Specific 

 Gravity of 

 Solution. 



H,0. 



Solu- 

 tion. 



HaO. 



Solu- 

 tion. 



HgO. 



Solution. 



H2O. 



Solution, 



NaCl 



NaCl 



KCl 



KCl 



MgCl^ 



MgCl^ 



CaCl2 



CaCl2 



1-03600 

 1-19320 

 1-04630 

 1-16990 

 1-03620 

 1-23380 

 1-27730 

 1-35110 



72-8 

 72-8 

 73-5 

 73-5 

 73-5 

 73-5 

 72-9 

 72-9 



77-6 

 85-8 



78-2 

 82-8 

 78-0 

 90-1 

 902 

 95-0 



78-8 

 78-8 

 79-5 

 79-5 

 79-5 

 79-5 

 78-9 

 78-9 



84-0 

 92-8 

 84-6 

 89-6 

 84-4 

 97-5 

 97-6 

 102-8 



181-7105 

 181-7105 

 181-7105 

 181-7105 

 181-7105 

 181-7105 

 181-7105 

 181-7105 



188-2521 

 216-8168 

 190-1237 

 212-5831 



188-2884 

 2241943 

 232-0987 

 245-5090 



181-7893 



181-7893 

 181-7900 

 181-7900 

 181-7900 

 181-7900 

 181-7894 

 181-7894 



188-3361 

 216-9096 

 190-2083 

 212-6726 

 188-3728 

 224-2918 

 232-1963 

 245-6118 



1-036013 

 1-193190 

 1-046310 

 1-169880 

 1036210 

 1-233796 

 1-277283 

 1-351080 



+ 0-000013 

 -0-000010 

 -0-000010 

 - 0-000020 

 + 0-000010 

 -0-000004 

 -0-000017 

 -0-000020 



§ 20. Serial Determination of the Specific Gravity of a Saline Solution. — The 

 method by which the specific gravity of a saline solution is determined with 

 the hydrometer is given in another place (see § 18), and it is there shown how the 

 total displacement of the instrument when floating in the solution up to the 50-mm. 



