62 



SCIENTIFIC AMUSEMENTS. 



in consequence, there is not enough water left to dissolve all the 

 salt present, some of the salt separates in the solid form as small 

 crystals. If too large a flame be used, the liquid will probably 

 "bump " violently. To avoid this, the flame should be small, and the 

 liquid kept continually stirred with a piece of glass rod. Table 

 salt is manufactured in this way from brine obtained naturally 

 from springs in the salt districts, or made by dissolving rock salt in 

 water ; the liquor is allowed to settle awhile to clarify it, and is 

 then evaporated down in pans by fire. The solution first becomes 

 saturated by the driving off of the water, and then salt deposits in 

 crystals. If the evaporating brine is kept well agitated, the 

 crystals formed are small, and make table salt ; but if the evapora- 

 tion goes on more slowly and gently, the crystals are larger. Bay 

 salt, used for curing fish, &c., is thus prepared in large crystals 

 J to J inch across. The salt as it separates is " fished " or raked 

 out of the brine pan by means of a ladle perforated with holes 

 forming a strainer, or by a sort of rake, so that the solid particles 

 of salt are retained whilst the liquid brine runs away. 



It is particularly noticeable that in this operation various im- 

 purities soluble in water, and contained in the brine along with 

 the true salt, become separated from the salt, the latter being 

 obtained pure in the solid form, whilst the former remain dis- 

 solved in the remaining liquid or 

 " mother-liquor." 



Expt. 56. To prepare Salt from 

 Sea- Water. Obtain a quart or so 

 of sea-water, and boil it down in an 

 evaporating basin holding half a 

 pint, adding more sea-water as the 

 liquid diminishes in bulk by evapora- 

 tion. By and by the liquor will 

 become so strong in salt that solid 

 crystals of salt will begin to form. 

 "When some little quantity has thus 

 separated, let the whole cool, and 

 separate the crystals of salt from the 

 mother-liquor by placing the whole 

 in a glass funnel in which a blotting- 

 paper "filter" is placed (fig. 36). 

 This filter is prepared by cutting a 

 piece of blotting-paper into a circle, 

 Fig. 36. Filtration through Paper. and folding this double, so as to form 

 a semicircle, then folding this again so as to form a quadrant, and 

 finally opening out the auadrant into a hollow cone, which is 



