1839.] Dr. JR. A. Smith, on Organic Matter of the Air, 89 



WEEKLY EVENING MEETING, 



Friday, March 25, 1859. 



Sir Henry Holland, Bart. M.D. F.R.S. in the Chair. 



Robert Angus Smith, Esq. Ph.D. F.R.S. 

 On the Estimation of the Organic Matter of the Air. 



After describing the opinions concerning organic matter in the air, 

 and the various attempts made to estimate the amount, the speaker 

 described a method of obtaining the relative quantity by means of 

 mineral chameleon, permanganate of potash or soda. This mineral 

 had been proposed by Forchammer, as a mode of estimating the 

 organic matter in water, but it was capable of estimating quantities 

 much more minute. At first the air was passed through the solution of 

 chameleon, but this was not found to cause complete action. It was 

 necessary that the air should remain for some time in contact with the 

 solution to be decomposed. It was then ascertained that the relative 

 amount of organic and other oxidisable matter in air could be found 

 by a simple metrical experiment in a few minutes. 



The speaker then said : — In working out this idea, it has been 

 found that a vessel of the capacity of 80 to 1 00 cubic inches is the 

 most convenient. This is equal to rather less than a quart and a half 

 and rather more than a litre and a half. 



The solution of chameleon used must be extremely weak, so that 

 small quantities cannot readily be distinguished by gaslight. 600 

 grains of it are required to decompose 5 grains of a standard solution of 

 oxalic acid. The standard solution of oxalic acid is so made that 

 1000 grains neutralize one grain of carbonate of soda. A thousand 

 grains contain therefore 1 * 184 grains of crystallised oxalic acid. 



To prepare the solution a manganate was formed by heating nitrate 

 and carbonate of soda and manganese, assisted by a little chlorate of 

 potash. There was the most minute trace of nitrate remaining in the 

 solution. Perhaps chlorate of potash would have been better, but I 

 had no idea at the time of the difficulty afterwards found in obtaining 

 the same quality. A solution of this manganate was made in pure 

 water, and carbonic acid passed through* until a reddish purple shade 

 was obtained. It was then tested by oxalic acid, adding three or four 

 drops of pure sulphuric acid. The purest water obtainable was added 

 to dilute it to the proper amount. This often failed ; and I have some- 

 times for a whole week failed to obtain the proper solution. Although 

 I call it permanganate, it is not entirely so ; it is a mixture of man- 



