40 
THE VOYAGE OF H.M.S. CHALLENGER. 
“ From 30 to 10 c.e. of sea-water was introduced into a thick porcelain crucible of 
k;i"wn weight, furnished with a tight-fitting cover, and evaporated in a water-bath. So 
>«>on as the silt was sufficiently dry, the crucible, with the cover on, was heated for 
about tiv. minutes over one of Bunsen’s gas burners, then cooled and weighed with its 
. ■ ■:.*■ nts. The free magnesia liberated was now determined in the manner described,” — 
■ a : by titration with very dilute standard solutions of hydrochloric acid and caustic 
alkali, using aurinc as an indicator. 
Tie method came to me far too late to help me in my work, but being curious to sec 
how it answers, 1 tested it by a few trials with analysed waters. 
Wati S iph 629 B., Oct. 22, 1874 ; lat. 5 44' N., long. 123° 34' E. (Laboratory 
number 332.) 
Water used = 4 0 9 84 grins. 
Ignited residue, 1‘3483 grins. 
Decinormal hydrochloric acid required for MgO = 31*2 c.c. = 3*12 x ^ [Mg] mgrms.* 
Hence (CL — 0) = 31*2 x 2*75 mgnns. = 0*0858 grm. and corrected residue = 1 ’4341 or 
. 4 1*92 grins, per kilo. The full analysis had led to the value 34797 for the total salts, 
• x lit'ivc *>f carl ionic acid.f The “chlorine,” per kilo, was 19*274. Hence real total 
'■dts am x 1 ‘8058 = 34‘804 ; deducting 0*152 for the carbonic acid per 100 of total 
salts, we have 34*751. 
The N nrwegian factor, 1*809 (which excludes the C0 2 ), leads to the number 34*8GG. 
H 'filer Sainplr 1259, Oct. 25, 1875; lat. 39' 1G' S., long. 124° 7' W. (Laboratory 
number 347.) 
Water used, 40*99G. 
Residue after 5 minutes’ ignition, 1*3970. 
Do. 10 „ do., 1*3680. 
Do. 15 ,, do., 1*3530. 
required, 26*1 c.c. of decinormal hydrochloric acid=71*8 mgrms. of (Cl 2 — 0). 
Hence corrected residue = 34*755 per kilogramme. 
By full analysis, t = 34*582. 
From the “chlerini . which was = 19*149, we have (exclusive of C0 2 ) — 
By my factor, . . . 34*52G 
By the Norwegian factor, . . 34*640 
cormUoi) wt. Unecec • he original alkalinity, amounta to only 0*07 c.c., and may, 
th*r* f'tr*, W neglected. 
• Cormtad f r the bromine an 4 a ulight over-determination in the aoda. 
