TRANSACTIONS OP THE SECTIONS. 
63 
raide of ammonium. It is true that a portion of gallnte of silver soon precipitates, but 
silver solutions of moderate strength always retain in solution a portion of the preci¬ 
pitant; and this fact lias been made use of by the author, Mr. Thomas and some 
others, by adding excess of moist iodide of silver to a new silver bath, to obviate the 
tendency it has to dissolve out the film of iodide of silver on the collodion plate.. 
When using a bromide as the sensitizing agent, bromide of calcium lias been found 
most effective; the nitrate of lime resulting from its decomposition in the silver bath 
having no detrimental action. The formula is as followsbromide of calcium, 
4grains; dissolve in spirit of wine 2 drachms; add rectified ittber G drachms, gun 
cotton quan. guff. The silver bath used must be GO grains to the ounce. The bro- 
m.ied collodion is tolerably rapid, mid, unlike most others, improves by age, even 
hejond n twelvemonth. The author lias used the following formula with a simple 
30-grain silver bath, and has obtained in all the varying conditions of light, whether 
of news or portraits, any amount of vigour desired:—The collodion : Take pure 
fcdide of potassium, any quantity; triturate this in a glass raortnr with spirit of wine, 
Jl over proof, Until the spirit is unable to dissolve more of the iodide. Tukc of this 
solution ;j parts; sulphuric ccthor, free from acid, 5 parts; mix and dissolve in it gun 
cotton, to form u tough and rather thick film. The developing agent is, pyro-gallic 
“cid, 2 grains; glacial acetic acid, 20 drops; spirit of wine, l drachm; watev to make 
»p 1 oz. 
On the Physiological Proper tic* of Curbazctic Acid. 
By Professor F. Crack Calvert. 
Hie author stated that lie had supplied some of this acid to Dr. Bell, Physician to 
the Royal Infirmary, Manchester, wiio had cured several cases of intermittent fever 
whit, He also said that he Bliould be very happy to furnish any physician with a 
iff" 9 uant ity of this substance, so that its real medical value might be ascertained. 
After describing the process by which puve carlmzotic could be procured from carbolic 
he impressed upon the Meeting the value of the pure acid as a yellow dye for 
0a the Action of Gallic and Tannic Acids on Iron and Alumina Mordants. 
By Professor F. Crack Calvert. 
fhe author drew the following conclusions from the facts contained in his commu- 
nication1st. That there can be no doubt that tannic acid is the matter in tanning 
whstances which produces black with iron mordants. 2ticlly. That the reason of gal- 
‘ c ac ‘d producing no black dye is, that it reduces the peroxide of iron in the mordant, 
wiling a colourless and soluble gallnte of protoxide of iron. 3r(lly. That gallic add 
“ the property of dissolving hydrate of alumina, and also of separating alumina 
mordants from the cloth on which they are fixed. 4thly. That the reason of extracts 
, * n,l, ng matter losing their dyeing properties is, that the tannin is transformed into 
n' IC . flc , ,"hilly. That gallic ucid possesses the property of dissolving iron, and 
' u ' a . VE c ' a jm to the character of atmc add ; whilst tannin, not having this action, 
bim to ho in reality a nentrul substance, fithly. lie also found that 2 to 
•- ft impure carbolic add added to extracts of tunning matters, such as those of 
JWch, quercitron hark, &c., completely prevented for several months the transfor- 
„ r . l01 ’ °' *be tannin which they contained into gallic acid, and thus rendered tannin 
e «racts commercially useful. 
r,.f -Action of Citric, Tartaric and Oxalic Acids on Cotton and Flax 
tores under the influence of Dry Heat and Pressure of Steam. Bip 
Professor F. Crace Calvert. 
' las observed that when two to four parts of these acids are dissolved in 
'vard l* 0 . , Wa t er » and linen or cotton dipped into the solution obtained, and after- 
Ihe tenant * r ? ie ^Gy, on exposure to certain temperatures, completely destroy 
1854 *' ° l t " e ™ re ‘ Pbis action of organic acids is interesting when it is known 
