42 



Eudiometer 

 tube. 



Manipulation. 



Maximum of 



diminution. 



Subsequent in- 

 crease; and why. 



The muriate is 

 preferable to tht 

 fulphate. 



ACCH'NT OF A NEW EUDIOMETER. 



opaque and almoft black. The procefs is apparently owing- 

 to a iimple elective attraction ; in no cafe is the gas decom- 

 pofed ; arjd under the exliaufted receiver it aflumes its elaflic 

 form, leaving the fluid with which it was combined unaltered 

 in its properties. 



The instruments neceflary for afecrtainirig the composition 

 of the atmofphere, by means of impregnated folutions, confiit 

 limply of a fmall graduated tube, having its capacity divided 

 into one hundred parts, and greatefl at the open end ; and of 

 a velTel for containing the fluid. 



The tube, after being filled with the air to be examined, is 

 introduced into the folution ; and, that the aclion may be more 

 rapid, gently moved from a perpendicular towards a horizontal 

 pofition. Under thefe cireumftances the air is rapidly diini- 

 nimed ; and, in confequence of the dark colour of the fluid, it 

 is eafy to difcovcr the quantity of abforption. In a few mi- 

 nutes the experiment is completed, and the whole of the oxi- 

 gen condenfed by the nitrous gas in the folution in the form of 

 nitrous acid. . 



In all eudiometrical proceffes with impregnated folutions, 

 the period at which the diminution is at a ftand rnuft be ac- 

 curately obferved ; for, fhortly after this period, the volume of 

 the refidual gas begins to be a little increafed, and, after fome 

 hours, it will often fill a fpace greater by feveral of the hun- 

 dred parts on the fcale of the tube, than that which it occupied 

 at the maximum of abforption. 



This circumftance depends upon the flow decompofition of 

 the nitrous acid (formed during the experiment), by the green 

 oxide of iron, and the consequent production of a linall quan- 

 tity of aeriform fluid (chiefly nitrous gas) * ; which, having 

 no aflinitv for the red muriate, or fulphate, of iron produced, 

 is gradually evolved, and mingled with the refidual nitrogen. 



The impregnated folution with green muriate is more rapid 

 in its operation than the folution with green fulphate. In cafes 



* The decompofition of nitrous acid, by folutions containing oxide 

 of iron, as its minimum of oxidation, is a very complex proceft. 

 The green oxide, during its converfion into red oxide, not only dc« 

 compofes the acid, but likewife a£h upon the water of the folution $ 

 and ammoniac is fometimes formed, and fmall portions of nitrous 

 oxide and nitrogen evolved with the nitrous gas. 



when 



