HUNTER ON THE EWECTS O F PRESSURE 7 G spongy iron is obtained by calcining with coal the residues from copper pyrites. Dr. Thudichum thought that the whole fungus theory was nothing better than a vague and wild surmise. l f r . Wariiigton That water which had passed through iron-sponge does not yield fungi on addition of sugar may be due to tlie removal of the phosphoric acid which had been retained by the hydroxide of iron wherewith the sponge is coverecl. As to the experiments with charcoal I wisli t o observe that water filtering through fresh charcoal takes away from it some phosphates but after the filter has been used for a time this will no more be the case. This circumstance may perhaps explain the difference in the observations of Messrs. F r a n k l a n d and Heisch.Dr. D~iprB asked wliether Dr. F r a n k l a n d and Mr. Heisch had boiled tlieir sugar-solutions bcfore mixing them with the waters to be examined? Whenever he (Dr. DuprB) did so he obtained no fungi. Dr. F r a n k l a n d replying [to Dr. DuprB] My sugar-solutions were not boiled but in Experiment No. 9 the water had been previously boiled for a long time and the sugar and all the other substances heated to a much higher degree than that of boiling mater and I obtained more splendid fungi here than in any other case. [To Mr. HBiscli.1 The difference in our obsermtions regarding animal charcoal appears t o be satisfiictorily explained b~ blr. V a r i n g t o n ’ s observations. As to the two fungi from sewage and from white of egg I merely pronounced them to be similar to but not identical with one another.I paid no particular attention to the emission of butyric smcll. [To Mr. Bell.] 1 investigated the effluent water about 24 hours after its collection. (Here Dr. Russell remarked that he had done the same.) [To Dr. Voelcker.] I have also found that sewage is apt to have its ammonia converted into nitric acid. IX.-Ou the Bfecfa of I”1.essw.e on tlie Absorption of Gases by Charcoal. By J O E N HUNTER N.A. F.C.S. F.R.S.E. Professor of Mathematics and Natural Philosophy University of King’s College Windsor Nova Scotia. IN the following memoir I purpose giving the results of a few obser- vations on the effects of pressure on the quantity of a p s absorbed by cocoa-nut charcoal.ON THE ABSORPTION UP GASES BY CFLiRCOAL. 77 The form of apparatus employed in ordcr to obtain pressurc in these experiments presents the great advantage of being casily taken to pieces and when very high pressures are not required I hive found it to work admirably. Two strong copper plates (a A) are connected by nieans of t h e e iron rods (T T T) firmly fisteiiecl t o the lower ancl passing tlirough holes in the upper plate \\here they are niade secure by screws aud nuts (B). Each plate contains a groore in n hich is placed a leather maslier covered on the exposecl sur- face with a mixture of white lead and gieLisc. 0 The ground ends of a thick glass cylinder are fitted against the leathers ancl when the plates are screwed together a strong joint i.; formcd capable of resisting a pressure of about fire or six atniosplieres.The pressure is produced by first filling tlie glass cylinder quite full of water T and then introclncing into it an iron screw (S) which works througli leather packing. In performing an experiment a vessel (V) containing mercury is placed on the lower plate. Two tubes are inverted in the mercury ; one partially filled with clry air acts as R manonieter; the othcr con- tains a fragment of cliarcoal and tlie grts under examination. The original volume of the gas is read off befoie introducing the cliarcoal into thc tube ancl after a sufficient time has elapsed the amount of absorption is carcfully determined. The glass c j liuder is tlm~ placed over the tubes and the upper secured to tlic lower plate by means of the screws.The interior of the apparatus is now filled with water and the pressure produced after the screw is measured by observing the volume of the air in the manometer tube. The corresponding diminu- tion in the volume of the gas in the absorption tube is also read off and since me know the original volume of the latter we can easily calculate what it ought to be a t each increase of pressure ancl the difference between the observed and calculated volumes gives the gbsorption. From the necessity of employing a comparatively small quantity of the gas in each experiment rarely more than 5 or G c.c tllc differences corresponding to each increase of pressure are not so regular as I could hare wished ; nevertheless in comparing the results contninccl in the following tables it may be observed first that the amount of absorption increases with the pressure to which tlie gas is exposed ; and secondly the same change of pressure produces about the same amount of increase in the quantity of each gas absorbed.It is worthy of observation that if we compare the relative wciglits VOL. SSIT. 11 HUNTER ON THE EFFECTS OF PRESSURE 78 of the absorbed gases in tlie following tables we find that cocoa-nut charcoal absorbs a greater weight of cyanogeii thnu of either amnionia or carbonic anhydride. In the tables of absorptions :- V = tlie volume of gns absorbed by one volume of cocoa-nut charcoal ai 0" C. a i d the corresponding pressure.P = thc pressurc in millemetres to Trhich the gas is exposed. First Scries. I P. 760 .O 1102 .o 1170.4 1367.2 1479.7 ~ ~~ P. 760 '0 1013.8 1095.9 1149.1 First Scries. V. 170.4 173 .O 176.9 178 '2 179.5 Fourth Series. v. 170 '6 171 .7 173 '0 176 '9 v. 78.2 91 '1 91.7 93.1 P. 760 .O 1009.3 1073.8 1333.6 1.150 5 9G .G Second Series. Third Series. ~~ v. v. lG5.5 l6G .4 173 .O 176.9 v. 172 .? 17s .2 i s 0 .a 193.6 191.8 187.3 190 .o 194 .o 197.5 201 '9 P. 760 .a 110k 3 117s .O 12G9 .2 1369.5 1496 '5 1796.1 2002 '6 2605.5 P. ?GO .O 1490.7 l(;Ss .1 2397 .O 2910 .8 3858 -2 P.850 .7 ?GO .O 1390 2 . 1639 -8 P. 760 .O 829 5 950.2 1021. .D 1112.9 l Z l i . 3 1343 .; 1499 .7 1693 9 1955 9 Third Series. P. - 760 '0 962 .9 10-15 .6 s92.4 1143.7 1262.2 1408 .O 1594.5 67 .i 9s .o l i 0 . 7 171.3 IiCi.0 173 2 180 '8 1s3 5 188 .7 196 .'7 209 '5 Fifth Series. Secoiid Series. v. G 1 . 7 81. .5 86 .O 102 '1 V. 71 '1 77.9 76 ' 9 77 -4 78.4 80 .o 51 '1 82.5 2143.4 88 .G Fonrth Series. P. 80 5 81.5 61 5 88 .0 8G 1 E5 .S First Series. v. 103.5 10G .8 107 7 109.9 112.8 114.5 116'3 129.2 v. ~ 760 .0 935 .G 1035 6 1155 9 150.3 3 130G.h 1778 4 2190.3 v. 106.7 107 .? 103 '5 109 .0 109.9 107.5 107.7 112 0 115 B Second Series. Fifth Series. v. 1 P. 132 4 P. 7G0 .O 1146.8 1510 .F 1886.3 2.103 .1 760 ,0 I llti9.G 1291 2 1628 8 1S73 I. 103.1 113 .0 220-1 ' 7 2678.2 P. 760 '0 GO .a 1051.1 1159 '9 1293 .5 1.163 '0 lGYl.9 19s0 .5 Fourth Serieg. P. 560 .0 1031.3 1101 .2 1182 .5 1 1276.0 1335 '5 1515.4 1865 .S 103 '2 105.1 106.8 108.5 110'3 111.3 112.2 113.3 v. Fifth Series. 1 P. s1 .0 1 1011.G 987 760 .Q 9 53 ' 2 8.5 5 57'3 9.5 5 1 1100 9 1113 8 1625 6 1912 0 I 232h 1 Third Series. P. P. V. 10G .G 111t.1 115 .0 117.1 11s .-J! Sixth Series. V. 102.5 103 4 10 1.7 106 k 113 0 119.3 79 7GO '0 1011.2 1143.3 1315.1 1ss0 '2 760 .0 1212.3 1338.4 19-$2 .5 1493 .4 2286 ' 8