BETWEEN THE VISCOSITY OF LIQUIDS AND THEIR CHEMICAL NATURE. 593 
If ethylidene chloride be used instead of ethylene chloride, a negative difference, — 25, 
as in most other series, is obtained for the effect of CHj. 
The fact, too, that methylene chloride is the lowest meml’er of the series, and 
contains onl}^ one carbon atom, may be important. 
The large differences brought about by the values for formic acid and benzene are 
further indications of the abnormal coefficients possessed by the initial members of 
homoloo-ous series. 
o 
Alcohols .—This series, as is the case under every condition of comparison, differs 
from all the others. An increment of CH^ not only exercises great influence on the 
viscosity coefficient, but its effect is exceptional, inasmuch as the sign changes as tlie 
molecular weight increases. 
The differences between the first three members are positive; all the others are 
negative. In the tertiary alcohols the effect of CHo is at a maximum, and reaches 
the large value of — 148. 
CoEEESPONDiNG Compounds. 
Iodide. 
Diff. 
Bromide. 
Diff. 
Chloride. 
Diff. 
Acid. 
Diff. 
Alcohol. 
V- 
'/• 
'/• 
Methyl .... 
399 
• • 
• • 
-137 
536 
70 
.329 
Ethyl .... 
371 
42 
329 
, , 
, * 
- 14 
385 
- 70 
441 
Propyl .... 
353 
28 
325 
51 
274 
34 
319 
-no 
463 
Butyl .... 
• • 
• • 
309 
• • 
405 
Isopropyl . 
359 
’ 30 
329 
54 
275 
-132 
491 
Isobutyl . . 
338 
27 
311 
31 
280 
31 
307 
-114 
452 
Allyl .... 
344 
29 
315 
53 
262 
< • 
- 29 
373 
Ethylene . 
514 
(52) 
410 
On comparing the coefficients of corresponding halogen compounds a marked 
regularity is apparent. The iodide has a coefficient which is Invariably larger, in 
general, by some 30 units, than that of the corresponding bromide, while the bromide 
has in turn a coefficient which is invariably larger than that of the corresponding 
chloride, in general by some 50 units. There is here a close connection between the 
molecular weights of the halides and the magnitude of their coefficients, whether the 
compounds be normal or iso alkyl derivatives, or allyl or ethylene derivatives. 
On comparing the acids with the iodides, the two lowest members exhibit a marked 
irregularity. Formic acid has a coefficient which is more than half as large again as 
that of methyl iodide, although the latter has the higher molecular weight. The 
coefficient of acetic acid is still larger than that of ethyl iodide, although the difference 
MDCCCXCIV.—A. 4 G 
