426 | Scientific Intelligence. 
The amount of water to be employed depends of course upon cireum- 
stances. With an apparatus of the given disnentionad from 25 to 70 litres 
of it were used according as the dae was of moderate size, or the appa- 
ratus ashen to its utmost capacity —(Poggendorff’s Annalen, cxii, 634). 
PHOTOG: 
12. 4 vad Collodion.—The ‘ Photographic Notes” publishes the fol- 
lowing esis for a collodion ten times more rapid than ordinary collodi- 
on, which is copied without comment in the Moniteur de la Photographie. 
Plain collodion, - - - 
Acetate of oc - - - - oa - 
This formula we fine “carefully titled and in our hase i poral ord 
lutely worthless. 
13. A rapid dry process. aaa Moniteur de la ong Fenpe for August 
gives a formula of Mr. Roman de Wesserling peat ae tia t's pro- 
cess and giving a dry oolladiod process as rapid as t 
It is essential to havea gun-cotton which gives a saael coliodion, 
and one also which is able to resist the repeated washings. The co 
must be neutral, The ether ought to be ep. gr. 0°732 and should not 
redden litmus paper, even after long immers 
For landscapes, and copying, a thick collodion i is first made as follows— 
‘5 gramme gun-cotton. 
90 cubic centimeters oe sp. gr. 0°732, 
cohol 95 per ct. 
Of an thick soticaloa take 40 parts and add 
5 parts ether, sp. gr. 0 
a5 “ alcohol 95 per ct. containing 
0°250 grammes lodid of ammonium. 
0°250 = cadmium. 
For ee the sete is Psi viz,— 
1 gramme gun-cotto 
90 parts sulph. ether 7 ¥ 0°732.— 
10 “ alcohol 95 per c 
ar filter the collodion, then take 
rts of this thick collodion, 
28 * alcohol containing 5 per et. iodid of cadmium. 
bromid of 
ium. 
15 aliases: 0-782. 
