230 THE FLOATING-MATTER OF THE AIR. 



izes ; in the other ten minutes' action fails to do so. 

 This latter interval indeed might be multiplied twenty- 

 fold and still prove ineffectual. Tn the one case the 

 process of boiling purged the liquid of its air ; in the 

 other case the air was retained within and above the 

 liquid. The case therefore connects itself with our 

 former illustrations. 



On the 21st of February six bulbs were charged 

 with fresh urine carefully neutralized and boiled for five 

 minutes in an oil-bath. Of the six flasks, four remain 

 perfectly clear and brilliant, one is slightly cloudy, and 

 one tiurbid. 



The urine here referred to was neutralized in our 

 own laboratory ; but as the importance of accurate neu- 

 tralization has been much insisted on, I wished to check 

 myself. At my request, therefore, Dr. Debus was good 

 enough to send me from Grreenwich a quantity of urine 

 carefully neutralized by him. On the 1st of March 

 seven retort-flasks were charged with the neutralized 

 liquid. These were boiled for five minutes in an oil-^ 

 bath and sealed during ebullition. Three of these flasks 

 have become turbid, but four remain perfectly clear. 



On the 5th of March Dr. Williamson was good 

 enough to send me a supply of neutralized urine collected 

 in a public urinal in University College. The colour 

 was very deep, the odour was very bad, and the precipi- 

 tation on boiling very copious. I'ourteen retort-flasks 

 were charged with this liquid on the 6th of March. 

 Seven of them have gone bad, but seven of them remain 

 clear. 



On the 10th of March Dr. Frankland was good 

 enough to send me a supply of urine neutralized by 

 himself. It was introduced into four retort-flasks, which, 

 like the others, were boiled for five minutes in hot oil 

 and sealed during ebullition. None of these flasks have 



