354 Chronicles of Science. ¥ [Apri], 
first with acid, then with alkali, and then adding nitro-prusside of 
sodium ; this communicates a beautiful violet colour. The next con- 
sists in adding sesquichloride of iron, which at once gives a purple 
red tint if hyposulphite be present. The third test consists in adding 
iodine and starch, the blue colour of which is immediately discharged 
on the addition of a few drops of a solution containing a minute trace 
of hyposulphite. This reaction is very delicate, as it is capable of 
detecting one grain of the salt dissolved in 2} gallons of water. The 
fourth mode of detecting hyposulphite is based on the property which 
it has of reducing sesquichloride of iron to the protochloride. The 
suspected liquid is boiled in a small flask, with four or five drops of 
the iron solution, and a drop of red prussiate of potash is added. If 
hyposulphite be present, a blue precipitate or coloration is produced. 
This will detect one grain of the salt in four gallons of water. The 
fifth and most delicate test of all is obtained by introducing a few drops 
of hydrochloric acid, and a fragment of zinc into the suspected liquid, 
and testing the evolved gas for sulphuretted hydrogen by means of 
lead paper. This is so sensitive that it will detect one grain of hypo- 
sulphite in rather more than seven gallons of water. For the purpose 
of detecting any hyposulphite in the finished picture, the plan adopted 
by Mr. Spiller is the most convenient; he moistens the white parts 
with a little protonitrate of mercury, when the presence of even a trace 
of hyposulphite is shown by the production of a brown or black stain. 
Few things are falsified more than the chloride of gold and the 
aurochloride of sodium used by photographers for toning their prints. 
The usual adulterant is common salt, which is sometimes added in ~ 
such quantity that a bottle professing to hold seven grains of gold 
sometimes contains only a little over two. The editor of the ‘ Photo- 
graphic News’ has published a very simple mode of detecting this 
adulteration. Both the chloride of gold and aurochloride of sodium 
are soluble in alcohol, whilst chloride of sodium is insoluble in that 
liquid. The photographer has, therefore, only to stir up the con- 
tents of a fifteen-grain tube with alcohol, and the amount of white. 
crystalline residue will show how much common salt has been sold to 
him at the price of gold. 
M. Quaglio, an engineer of Vienna, has investigated the properties 
of oleate of silver, or silver soap, in photolithography. After some pre- 
liminary preparation, the lithographic stone is covered, with the aid of 
a flannel rubber, with the silver soap, and it is then exposed under a 
negative to the sun. The portions unacted upon are then dissolved 
out with naphtha, and the stone is ready to be gummed and inked 
in in the ordinary way. This process is extremely easy and appears 
likely to be successful. The impression is obtamed direct from a 
negative, a transparent positive not being required, as in some other 
processes. 
The substitution of a less expensive metal for silver has been the 
dream of photographers for many a year. M. Liesegang describes, in 
the ‘ Moniteur de la Photographie,’ a process devised by M. Obernester, 
of Munich, which seems to be very successful. The paper is first wasked 
