128 DONALD J. MATTHEWS. 
other than phosphoric acid, perhaps as phosphites or as an organic com- 
pound, which is oxidised to phosphoric acid by potassium permanganate. 
The ratio of phosphoric acid found in the untreated sample to the 
total shows a tendency to constancy, but it has not been determined yet 
whether the permanganate method converts the whole of the phos- 
phorus into phosphoric acid, and experiments on this are in progress. 
The samples of sea-water, with two exceptions, were taken at the 
Knap Buoy, half a mile outside the lighthouse on Plymouth Breakwater. 
The other two were taken close to the rocks under the Laboratory. 
The results are given in the following table, and also the method by 
which they were obtained. 
The salinity was determined against the International Normal Water. 
SURFACE SAMPLES TAKEN AT THE KNAP BUOY. 
| P20s5, mg. per litre. 
Date. G. Med. SAS Method. 
Found in duplicates. | Mean. 
1915 | 
April 21 | 10.30 a.m. | — _ | Iron and gravimetric == O-1 
i) 23 age ae. ” ” cad i O-1 
June 21 | 10.30a.m.| — <i < — 0-049 
July 5 noon — Ks Ms — 0-064 
minke | 10:30 a.m... .— Be - — 0-09 
se) 40 a.m. | 34°83 iy fp — 0-082 
Sept. 13 | 11.30 a.m. | 34-92 e x —- 0-04 
» 21 | 10.30 a.m. | 34-96 | Ammonia and colour — 0-046 
Nov. 24 | 11.35 a.m. | 34-78 - es 0-042, 0-041 |0-0415 
» 26 | 11.45 a.m. | 34-43 3 a 0-040, 0-034 | 0-037 
eee wt dOa.m. | 34-14 : », 0-040, 0-037  |0-0385 
Dec. - 2 | 12.20 p.m. | — hs - 0-0484, 0-0435_ | 0-0460 
SP 209 10:30! ames eo 1-46 5 “s 0-049, 0-047 | 0-048 
sf eS IES Oha mi, 1) = pe fa 0-044, 0-041 |0-0425 
9 LOM 210ip:m-~ | 26-20 se ” — 0-045 
5, 20 | TEe25-a.am. | 2969 , 55 0-058, 0-064 {0-061 
1916 
Jan. 3 | 11.35 a.m. | 25-66 5 3 0:057,- 0-Ob7 wa U-@am 
» 14] 1.55 p.m. | 33-87 | Iron and colour 0-0318, 00316 | 0-0317 
» 18 | 2.30 p.m. | 33-93 e 4 0-0336, 0:0348 | 0-0342 
eee ble 20ra.m. | 33°42 a ¥e 0-0378, 0-0391 | 0-0384 
Feb. 5 | 12.30 p.m. | 31-58 | a. if 0-0507, 00414 | 0-0460 
SURFACE SAMPLES TAKEN UNDER LABORATORY. 
1916 | 
Jan. 7 — — | Iron and colour 0-0602, 0-0572 | 0-0587 
Feb. | 11 — — a3 - 0-0408, 0-0421 | 0-0414 
