This solution differs only from the positive bath, by omitting the _nitric acid_: in all other respects it is precisely the same, and is prepared by the same formula, as given at page 64. This is called the _neutral bath_, and is best adapted to the negative process. The nitrate of silver employed in its preparation should be perfectly free from excess of nitric acid, otherwise the whole solution will be slightly acid. If it should not be convenient to obtain nitrate of silver without this objection, the acid may be neutralized by putting into the solution a small quantity of common washing soda-- say 1 grain to each 100 grains of nitrate of silver--previously dissolved in about half an ounce of water. This may be put in at the same time that the iodide of potassium is, and it would save one filtration. In twenty samples of nitrate of silver that I have tried the above quantity of soda has been found sufficient; if, however, the _white_ precipitate first formed is re-dissolved on shaking the mixture, free nitric acid is present, and more of the soda may be added. This bath will improve by age, and be less liable to fog after having been in constant use for one or two weeks. Operators who have the means, and design following the art professionally, will find it to their advantage to make from two to three times the quantity of solution they require for immediate use: by this means they will be enabled to replenish their stock, which may be used up or otherwise lost. PRACTICAL DETAILS OF THE =PRINTING PROCESS.= CHAPTER VI. PRINTING PROCESS--SALTING PAPER--SILVERING PAPER--PRINTING THE POSITIVE--FIXING AND COLORING BATH--MOUNTING THE POSITIVE. The Printing Process. [Sidenote: MANIPULATIONS OF THE PRINTING PROCESS.] There is probably no department of the photographic art where can be found an equal amount of variety, as regards chemicals, manipulations, etc. The course adopted in the commencement, of giving only one process for the operator to work by--and that a good one--will be strictly adhered to in this place. I have produced as good positives on paper by the following plan, as I have ever seen. Should the reader wish more extensive acquaintance with the printing processes, he is referred to Humphrey's Journal. Salting Paper. Water 1 quart. Muriate of ammonia 65 grains.