33 6 APPENDIX 



THE PREPARATION OF SOLUTIONS OF DIFFERENT 

 CONCENTRATIONS 



In the following formula, which is convenient for ordinary pur- 

 poses, the contraction which follows the mixing of solutions of 

 salts with water is not taken into account. This contraction in 

 the case of inorganic salts is very slight, and even in preparing 

 various "grades" of alcohol for the usual dehydration purposes 

 the following method is sufficiently accurate, 



.. V'b T/ , Va 



V= or V = — r . 



a b 



Where V equals the volume of the stock solution to be taken, 

 and a its per cent, of concentration, while V equals the volume 

 to which V\s to be diluted to bring it to the desired per cent. b. 

 V — Fwill equal the amount of water to be added to V. 



Where the specific gravities of the liquids to be mixed are 

 known the following formula may be employed ■} 



If D is the sp. gr. of a solution of the volume V a certain 

 volume x, of the second solution with a sp. gr. of d must be 

 added to bring the resultant mixture to the desired density d' . 



Thus 



V(D-d') „ VD + xd 



x = —±- -j-L or d' = —-L . 



d'—d V+x 



FREEZING MIXTURES. 

 Mixed with ioo parts of snow or powdered ice at approxi- 

 mately o° C. the substances enumerated below will give about the 

 following temperatures : 



Sodic carbonate (cryst.) 20 parts — 2°C. 



Potassic nitrate 13 



Potassic chloride 30 



Ammonic chloride 25 



Sodic chloride 33 



Calcium chloride (cryst.) 143 



Sulphuric or nitric acid (dilute) .... 100 



1 From Chemiker Kalendar. Biedermann. 



-15° 



-21° 

 -50° 

 - 4 0° 



