280 Scientific Intelligence. 
The standard acid. The use of crystallized oxalic acid, as suggésted 
by Mohr, has come into general favor, and nothing can be more satis- 
factory when the acid is pure and of constant composition. It is, however, 
difficult not only to procure a pure acid, but also to esses it dry with- 
out loss of erystal-water. To dry the pulverized acid over oil-of-vitriol 
until it ceases to lose weight, as proposed by Erdmann, or to select unef- 
floresced crystals by help of a magnifier, is tr ee re likely to in- 
troduce error. We employ a dilute sulphuric acid, w may be made 
of convenient strength for ordinary use, by diluting ten para ccatennn 
of oil-of-vitriol with water to the volume of a | 
The standard alkali is made from huwandal Caustic potas: yes 1s 
~~ in water and diluted until a given volume e. utral- 
izes 4 to 5 ec. c¢, of the standard acid, as is Niet; oe a ike aa 
tria als. 
e alkali-solution thus obtained is heated to boiling in a flask, and 8 
little freshly- -slaked — is added to decompose any earbonate of po 
e boiling is continued a few minutes and, finally, the ley is poured 
upon a filter, and the filtrate i is collected in the bottle from whieh it isto be 
used. Care should be taken to bring upon the filter some of the excess 
of lime that is suspended in the liquid, so that the latter may acquire 
no carbonic acid from the air. The clear liquid thus —s is a pot 
ash-lye containing lime in solution. If exposed to the air, the carbonic 
acid that is absorbed separates as carbonate of lime, Joie the liquid 
perfectly caustic. 
It now remains to determine with the greatest accuracy, Ist, the vol- 
ume of alkali which neutralizes a cubic centimeter of the _ and, 2d, 
the amount of SO, contained in a cubic centimeter of the 
"tno of 
The he kno wl 
Jour. Air Prakt. Chin, Ixxxiv, p. 424. Tincture of cosine is prepa 
by digesting ee frequent agitating three grams of pulverized cochi a 
in a mixture 0 cubic centimeters of strong alcohol with 200 oe 
distilled eaten, is ordinary temperatures for a day or two. The soluti 
On caper 
ora 
ae be 
of strong acid and acid salts make it orange or yellowish-orang® 
To determine the eee Repel be the alkali and acid, 4 8! 
volume of the latter, e. g. 20 ¢. ¢., is measured off into a wide mow 
flask, ten drops of scaiiaabliaidaes me “about 150 c. c. of water 1 : 
added—the alkali is now allowed to flow in from a burette, unti 
yellowish liquid in the flask, suddenly, and by a single drop, acquires 
violet-carmine tinge. 
In nicer determinations, it is important to bring the liquid a fo- 
‘to a given volume, by adding water after the neutralization is nea y 
- For this purpose, two or more flasks of equal —, waged 
and on the outside of each a strip of paper is gummed 
