[2] (2) Urine after filtration through sawdust.
'Physical Characters.—(1) Pale yellow, clear, with a slight opaque zone from mucus, normal urine odour.
'(2) Dark mahogany-brown colour—markedly opaque and somewhat turbid. A peculiar woody (resinous) odour, faintly ammoniacal.
'The "two ammonias" cannot be estimated by Wanklyn's process in the fresh urine, where there is so much urea, but in the filtrate they amount to—
| 0·032 | Free and saline | } | per 1,000 |
| 0·0016 | Organic | } |
I have kept two test-tubes half filled with (1) and (2), tightly corked, in the warm cupboard of the laboratory for the past three weeks; the sample of fresh urine has become offensive, but that of the filtered urine is perfectly sweet, and rather pleasant to smell.'
The filtrates from sawdust were a very dark brown colour, like 'stout' or 'porter,' and these have been evaporated to dryness without offence, and have shown no tendency to putrefy.
Experiments conducted in the same way with peat have yielded a filtrate almost identical in appearance to the sawdust filtrate, inoffensive on evaporation and not putrescible. The filtrates from peat and sawdust were always of $1m> than the urine added.
In order to ascertain how much urine could be got rid of by evaporation, I tried the experiment of using a flannel bag filled with sawdust or peat, and I found that with regard to one of these experiments (the bag being hung under a shed in the open between June 15 and July 20, 1895), only 81 ounces of filtrate having the qualities above given were obtained from 729 ounces of urine added to the filter. In this case 648 ounces of urine (over 40 lbs. weight) disappeared. In another experiment carried on in my room at University College I added (between May 9 and July 26) 626 ounces of urine, and obtained only 54 ounces of filtrate, so that in this case 572 ounces (nearly 36 lbs. weight) of urine had disappeared.
As far as my experiments have as yet gone, I have not discovered the limit of sawdust for dealing satisfactorily with urine. Thus in 1894 I filtered during May, June, and July, 39 lbs. weight of urine through 6 lbs. of sawdust in a flannel bag, and neither filtrate nor sawdust was in the least offensive. In the same months in 1895 I passed an additional 41 lbs. weight of urine through the same sawdust in the same bag, and practically with the same result. In 1896 I added over 30 lbs. weight of urine to the same sawdust, but as the flannel bag had become too rotten to hold together, I was obliged to have recourse to the metal filter-vessel. The early filtrate obtained in 1896 had a specific gravity of 1·061, but, like its predecessors, could be evaporated to dryness without offence, and the sawdust was not in the least malodorous, although it was distinctly (as it always has been in these experiments) ammoniacal.