1890 - 91 .] Mr J. Y. Buchanan on Sulphur in Marine Muds. 31 
thoroughly shaken up, then run into a narrow graduated cylinder, 
holding 50 c.c., which was emptied into the flask and then washed 
once into it with distilled water. To each of the flasks was then 
added 10 c.c. of the reddish-brown hut still acid, ferric sulphate 
solution, and the contents shaken. In a few seconds the black 
colour of the sediment had disappeared entirely, being replaced by 
a yellowish-red precipitate, which disappeared for the most part on 
the addition of dilute sulphuric acid. Water was then added to 
bring up the volume to 250 c.c., and the titration was effected with 
permanganate of potash solution ^1 litre containing grms.^ 
The three portions of 50 c.c. required each 1 1 *6, 1 1 *6, and 11 -7 c.c. 
permanganate respectively. We see then that a suspended pre- 
cipitate can be measured off about as accurately as a dissolved 
salt. 
It is evident, then, that if we have a mud containing FeS and 
other ferrous compounds decomposable by HC1, we can determine 
first the FeS by adding Fe 2 Cl 6 and titrating a portion with perman- 
ganate; then the other ferrous compounds, by adding HCland titrating 
another portion with permanganate, due account being kept of the 
weights and volumes used. In order to try the method in practice, 
three soundings were made ; — on 30th September 1881 in the Sound 
of Raasay, off Croulin Island, 120 fathoms ; and on the 1st October 
1881 in Loch Duich, in 49 and 51 fathoms. The first of these re- 
presents more or less the conditions in the open sea of coast waters ; 
the last two represent the conditions in a semi-enclosed loch basin. 
The Sound of Raasay mud was a light grey mud, with no offensive 
qualities. Both samples from Loch Duich were very foul smelling. 
All three samples were tightly stoppered up in their wet condition, 
and examined on 20th and 21st October 1881 in my laboratory in 
Edinburgh. I unfortunately had no suitable* ferric solution afloat 
with me so as to treat them immediately. In the three weeks that 
both muds from Loch Duich were kept in bottles, the surface layer 
got completely oxidised, and on opening the bottles the smell was 
gone ; but, on breaking through the surface layer, the unaltered 
black mud was exposed with all its original qualities, including its 
peculiar odour. 
The following was the method used in the case of the Loch Duich 
