251 
Test No. 2—The number of grams to separate the disk from water 
Dian .C: 
APTS a LR ae hs coeest oad ahty Peer RRC RENAE NC acl RE RIC 48.710 
EIN TeieaN cote Sweety naleael siete ayesaiterewcloiein) & uso, exauoesl cusnane payee s 48.715 
ADT OTES LS, 5 cach Che oes LOVES CREO CIR Sto RC I Bea eae an 48.725 
MINT EAE A ees Acta choredouct ots nus case ce waisla ss onaloe aero eusvasdvasccelune 48 .730 
MVERAGE Mo lerahicie te Pate ae sorts 48 .720 
Test No. 3.—The number of grams to separate the disk from water 
agents ©. 
TCTs T alee len gecoviey ocronelotck c coisvere ln oka i ites ober ob rctarareueretc Suacane evs 48 .630 
MURTHA es Neots ben ardt secs avatersiars Biya eusieiseaua nn orbies w wee PSS, BIE Bie 48 .640 
Terrien eves epaere cueva oO ensterscera wisieistnuctavee'o ecote ile level or ard maecete 48 .655 
ETGTeT ANA mes, koe tat teelsg tee sae ttt Corevehane elctete eateries ore Sarees cones 48.675 
PAVIOTAS Cl segcte cist sug Mitre te eel Oe eee, Snes enale. pie aL eters 48 .650 
The diameter of the disk being 10.6898 em,, the radius being 5.8449 
cem., the area is 89.7200 square em. In the first test given above it required 
0.5431 g. to separate one square cm. of water. In the second 0.5430 g. 
and in the third 0.5421 g. The average of the three tests is 0.5427 g. per 
square cm., which is equal to 531.846 dynes per square cm. 
In comparing these results with those of Gay-Lussac we find that he 
used a disk which was 11.86 cm. in diameter, and that it required 49.40 g. 
to separate the disk from water, or 526.875 dynes per square cm. 
At this point it may be well to state the precautions taken in the ex- 
periment. First, in order to insure that the water used was chemically 
pure, ordinary laboratory distilled water was redistilled in Jena glass 
vessels in the presence of sulphuric acid and potassium dichromate. Sec- 
ond, the disk was thoroughly cleansed by washing in a solution of po- 
tassium dichromate and sulphuric acid; then in alcohol; then the disk 
was dried in a current of air and washed again in redistilled water. Third, 
a delicate laboratory balance with a rider weight was used in the experi- 
ment. 
At the time the above data on the cohesion of water was worked out 
it was suggested that certain dissolved salts have a marked effect upon 
the cohesion of water. It is the purpose now to note some of these effects. 
A number of solutions of certain salts in distilled water have been 
tested by means of the same glass disk as used in the cohesion of water 
experiment. The first solution tested was that of sodium chloride. Six 
