TRANSACTIONS OF THE SECTIONS. 59 
effectual poison to the weaker forms of vegetation, or that when a soil is continually 
watered with a weak solution of salt it gradually accumulates in it until the soil be- 
comes sufficiently contaminated to be unfit to support vegetable life. In either case 
an interesting subject of inquiry is suggested—What is the weakest solution of salt 
which can produce this poisonous effect? or in other words, at what degree of dilu- 
tion does the danger cease? For salt is an important natural constituent of much 
spring-water, quite independent of any infiltration from the sea, as in this instance. 
' Thus, the water of the Artesian well, Trafalgar Square, London, con- 
tains in each gallon about ......+0+00 peeyettns eae Seca paveaneaner eck) 20°0 grains. 
That at Combe and Delafield’s brewery ....s.seresecereees Piendeisherersexey W200 oy 
That at Woolverton Railway Station ...... GALE Io ee apee sat ceubiee ma nga DORON Vay 
One lately sunk at Southampton for supplying a private manufactory 40°0 _,, 
May it not be asked whether the subject of the suitableness of waters in general 
for the various purposes to which they are applied,—be it in manufactures.or for 
steam-engines, domestic purposes or drinking,—is not worthy of a greater share of 
scientific attention than it has hitherto commanded ? 
Ona New Process for analysing Graphite, Natural and igi Uiigan By 
Professor R. E. Rocers, and Professor W. B. Rogers, University of 
Virginia. 
The present abstract will be limited to a brief statement of the principal steps of 
the new process, and such reference to the results as is necessary to give assurance 
of its accuracy. The details of the operation, with a description and drawing of the 
apparatus employed, will appear in the forthcoming number of the American Journal 
of Science. 
The extreme obstinacy with which graphite, natural as well as artificial, resists 
1 ‘oxidation by liquid re-agents is shown by the fact that neither nitric nor sulphuric 
acid, used singly, even with the aid of heat, produces any sensible effect upon the 
flakes of this substance. Schafhaeutl succeeded in oxidating scales of artificial 
graphite by surrounding them with boiling sulphuric acid and then dropping concen- 
trated nitric acid upon the liquid, but the action was so slow as to require several suc- 
cessive digestions of the same specimen to dissipate the whole of the carbon. 
_ The new process is founded on the fact that a mixture of bichromate of potassa 
and sulphuric acid, when applied in great excess to very minutely-divided graphite, 
converts the carbon rapidly and completely into carbonic acid. The fact of such a 
reaction was noticed by us more than two years ago, but the details of the present 
process were not matured until the winter of 1847, since which time we have used it 
in a number of instances for determining the carbon of graphite, and always with 
consistent and satisfactory results. 
Our method of proceeding is briefly as follows :— 
1. Apparatus used.—The object of the experiment being to convert the carbon of 
the graphite into carbonic acid, and by absorption to collect the whole of the latter, 
with the view of deducing from it the weight of the carbon, the apparatus is con- 
‘ structed of the following parts :—First, a retort for receiving the powdered graphite, 
bichromate of potassa, and sulphuric acid ; second, a large drying tube cf chloride of 
calcium to arrest moisture; third, a Liebig tube charged with standard solution of 
_ potassa followed by a small U-tube of fragments of potassa, both designed for the 
detention of the carbonic acid evolved; fourth, an additional U-tube to arrest the 
Moisture which might otherwise pass backwards from the aspirator; and, jifth, a 
large aspirating apparatus, to be used at the close of the experiment, The neck of 
- the retort is bent upwards at right angles and enclosed in moistened cloth or by a 
glass refrigerator, to prevent the passage of sulphuric acid yapour into the chloride 
of calcium. 
_ 2. Preparation of the Graphite—To ensure a prompt and complete result, the 
graphite must first be brought to the most minute division, This cannot be effected 
by triturating it alone, but is readily done by grinding it with pure quartz sand, or 
what is better, with small fragments of granular quartz, adding this substance in suc- 
cessive portions during the grinding, until it amounts to some thirty times the weight 
