178 NOTES. 



It produces deep red fumes as soon as it comes in contact 

 with the air, by combining with the oxygen of the latter 

 to form hyponitrous acid. Binoxide of nitrogen is com- 

 posed of two parts oxygen and one part of nitrogen; 

 hyponitrous acid is composed of one part of nitrogen and 

 three parts of oxygen. 



LECTUKE IV. 



( 17 ) Page 91. Chlorate of Potash and Sulphuret of An- 

 timony. Great care must be taken in mixing these sub- 

 stances, as the mixture is dangerously explosive. They 

 must be powdered separately and mixed together with 

 a feather on a sheet of paper, or by passing them several 

 times through a small sieve. 



( 18 ) Page 92. The mixture of chlorate of potash and 

 sugar does not require the same precautions. They may 

 be rubbed together in a pestle and mortar without fear. 

 One part of chlorate of potash and three parts of sugar 

 will answer. The mixture need only be touched witli 

 a glass rod dipped in oil of vitriol. 



( 19 ) Page 92. Two salts dissolved in water. Sulphate 

 of soda and chloride of calcium. The solutions must be 

 saturated for the experiment to succeed well. 



( 20 ) Page 96. Lead pyrophorous. This is tartrate of 

 lead which has been heated in a glass tube to dull red- 

 ness as long as vapours are emitted. As soon as they 

 cease to be evolved the end of the tube is sealed, and it 

 is allowed to cool. 



( 21 ) Page .99. Ckm cotton is made by immersing cot- 

 ton-wool in a mixture of sulphuric acid and the strongest 

 nitric acid, or of sulphuric acid and nitrate of potash. 



