360 FREEZING MIXTURES. 



A. Yes ; in very many ways. For 

 example a bottle of water wrapped in 

 cotton, and frequently wetted with ether, 

 will soon freeze. 



Q. Why would WATER FREEZE if the bottle 

 were kept constantly wetted with ETHER ? 



A. Because evaporation would carry 

 off the heat of the water, and reduce it 

 to freezing point. 



Q. Why does ETHE nfreezeunder the RECEIVER 

 of an kin-pump, when the air is exhausted ? 



A. Because evaporation is very 

 greatly increased by the diminution of 

 atmospheric pressure; and the ether 

 freezes by evaporation. 



FREEZING MIXTURES. 



1. If nitre be dissolved in water, the heat of the liquid 

 will be reduced 16 degrees. 



2. If 5 oz. of nitre, and 5 of sal-ammoniac (both finely 

 powdered) be dissolved in 19 oz. of water, the heat of the 

 liquid will be reduced 40 degrees. 



3. If 3 Ibs. of snow be added to 1 Ib. of salt, the 

 mixture will fall to (or 32 degrees below freezing point). 



The two following are the coldest mixtures yet known: 



1. Mix 3 Ibs. of muriate of lime with 1 Ib. of snow. 



2. Mix 5 Ibs. of diluted sulphuric acid with 4 Ibs. of 

 snow. 



Q. Why is it more easy to SWIM in the SEA 

 than in a RIVER ? 



