Marine Muds and Nodules 149 



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 but 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 perman- 

 ganate of potash solution fl litre containing - grms. j . 



The three portions of 50 c.c. required each n-6, n-6, and 

 ii'7 c.c. permanganate respectively. We see then that a 

 suspended precipitate 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 permanganate; then the other ferrous compounds, by 



adding HC1 and 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 3oth September 1881 in the Sound of Raasay, 



'nml in Island, 120 fathoms; and on the ist October 1881 



i.och Duich, in 49 and 51 fathoms. The first of these 



<-sents more or less the conditions in the open sea of coast 



waters; the last two represent the conditions in a st*mi- 



enclosed loch basin. The Sound of Raasay mud was a light 



grey mini, with no offensive qualities. Both samples fmm 



i Duirh were very foul smelling. All three samples were 



tightly stoppered up in their wet condition, and . 



on 2Oth and 2ist October 1881 in my laboratoiv in Kdmhurgh. 



I unfortunately had no mt.iMe ferric s<>lnii"n .dltMt with 



me so as to treat them immediately. In tin tin 



that both muds from Loch Duich wrre kept in bottlrs, the 



r got completely oxidised, and on opening the 



bottles t M was gone; but, on l>i >ugh the 



ace layer, the unaltered Mark mud was exposed 



ritual 'jiialitie-. in. hiding it- p.-. nliar odom . 



