18130 



Scientific Intelligence, 



301 



Article IX. 



■SCIENTIFIC INTELLIGENCE I AND NOTICES OF SUBJECTS 

 CONNECTED WITH SCIENCE. 



I. Neiu Salts of Lead. 



Chevreul has lately examined some salts of l^ead wliich had 

 been originally discovered by M. Proust, and in which he had 

 conceived that there existed an oxide containing less oxygen tiian 

 the yellow oxide. 1 afterwards examined the same shUs, and 

 found that they contained the common yellow oxide. Chevreul 

 has found that the acid combined with the oxide in these salts is 

 not, as we had supposed, the nitrate^ but the nitrous acid. This 

 is what distinguishes them from the nitrates of lead formerly 

 known. I shall here give a sketch of the results obtained by 

 Chevreul. 



1. There are tv/o nitrates of lead. 1. The common octahe- 

 dral nitrate, which is a supernitrate, containing an excess of 

 acid. 2. The neutral nitrate, composed of scales. It may be 

 formed by boiling together a mixture of yellow oxide of lead and 

 octahedral nitrate. 



The supernitrate of lead is composed of 



Acid 33 100 



Yellow oxide 67 203 



The scaly or neutral nitrate is composed of 



Acid 19-86 100 



Yellow oxide 80*14 403 



So that the quantity of oxide in the neutral salt is twice as great 

 as in the supersalt, 



2. Three hundred and fifty parts of water, 4 parts of super- 

 nitrate of lead, and 6 parts of lead, were boiled in a flask for 14 

 hours : 5*4 parts of the lead were dissolved. The liquid became 

 at first yellow, but the yellow colour gradually disappeared, and 

 a greyish white matter precipitated. The glass v/as attacked* 

 The grey matter consisted of a mixture of silica and hydrate of 

 lead. The lead amounted to 0*47 of a part of yeliov/ oxide. 



3. The liquid deposited needle-form crystals, which weighed 

 $•95. The mother water contained nitrate of potash. 



. 4. By this process the nitric acid is decomposed, and coo- 

 verted into nitrous acid and nitrous gas. Two salts are formed^ 

 one in plates (a nitrite), and one in needles (a subnif' / 



.5. The nitrite is best prepared by causing a c? .nt of caf- 

 bonic acid gas to pass through the solution of the ii^onitrite, 



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