From the Report of J. Lawrence Smith, United States Commissioner to Paris Exposition. METHODS AND PROCESSES OF MANUFACTURE. Burning tlis 8ulp!mr—Sulphur Furnaces.—It is not necessary to dwell upon this part of the subject, from the fact that there are so many various ways, each said to be excellent, for securing the combustion of the sulphur used for the manufacture of acid. Reference will be made simply to the principles involved in the best form of furnace. It is better to have one large than many small furnaces (called the sulphur furnace), and to have all the sulphur used for one day's combustion (say from one to four tuns) introduced at one charge, and to have just sufficient air admitted to keep up the combustion without heating the mass too much, as thereby more sulphur is volatilized. The vapor from the sulphur furnace should pass.to the combustion furnace, in which sufficient air is admitted to complete the combustion, allowing an excess of about two to three per cent of oxygen. From the combustion furnace the sulphurous acid therein formed passes to the niter oven, and from thence the mixed vapors pass into the lead chambers. Lead Chambers.—Too great care cannot be given to the construction and working of the sulphuric acid chambers. The plumbers should be required to distribute the straps uniformly, and not to have too great a strain on any one, as the lead of the chamber is often torn by the' neglect of this ; the chambers should be kept in perfect repair andfree from holes, or otherwissLthe sulphurous acid is lost in greater or less qtjantity. ?Vhere repairs are neglected, the practical yield with the same amount of material may range in throe years from 83 to 68 per cent of product. The sulphur is not often lost from an incompletecon version of the sulphurous into sulphuric acid by too little steam; too much air, and an insvifficient quantity of niter, but more frequently from too little chamber space to the amount-of sulphur burnt. In connection with lead chambers it is interesting to refer to the chambers of Kuhlmaun, of Lille, that prince of industii:.! chemists, the neatness and cleanliness of whose immense works are only excelled by the skill exercised and the purity of the articles manufactured. His chambers have a capacity of about 88,000 cubic feet. There are six different compartments, the first a small one, which is a cooler and purifier ; the second a small denitrifying chamber ; the third a small nitrification chamber ; the fourth a large chamber ; and fifth and sixth small c ambers, called the tail chambers. Nitric acid is employed for oxidizing, which is introduced into the third chamber, in a small stream divided into a spray by convenient arrangements. The circulation of the liquid acid proceeds from chamber five, which opens into chamber six ; from this it fiows into the largo chamber, which receives also the acid from the nitrification chamber; the acid collected in the large chamber ultimately passes into the denitrification chamber before it reaches the evaporating pans ; to secure a perfectly regular distribution of steam through the whole system, irhe lead pipes which deliver it into the chambers are provided with platinum nozzles, which prevent the orifices of the tiibes from gradually collapsing. Some of the chambers in Lancashire have over 100,000 cubic feet capacity ; and, as a general rule, the larger the chamber the better the proportioned yield. One of the most important problems in the improvement of sulphuric acid chambers is to produce chambers of small dimensions capable of producing the greatest amount of sulphuric acid free from arsenic. To diminish the amount of capital in establishing a lead chamber for this acid, multiplies their number, and brings an article requiring a certain amount of useless water and bulky receivers nearer to the consumers, diminishing the cost of transportation. At Bordeaux, Fournet has established the manufacture of sulphuric acid in a manner that deserves special attention, as it looks toward this economy just referred to. By means of apparatus skillfully arranged, in which the gas is made to circulate'more than once in pipes filled with coke, so as to bring about an intimate mixture, and then passing it into a small lead chamber, Fournet has succeeded, with a chamber of only 12,000 cubic feet, in burning 1,000 pounds of sulphur a day, and obtaining a yield of three tuns of sulphuric acid, an amount nearly equal to the theoretical yield. (To be contintied.) Uryins Oils for Varnlsli. In a recent work on varnish, by Violette, he quotes as follows from a celebrated manufacturer : " The oil is allowed to stand in a reservoir of lead for one or two months, after which the upper three quarters of it are drawn off to make drying oils for varnish, while the one fourth remaining at the bottom of the tank can be sold to grind paints, it being utterly unfit for varnish making. This settling of the oil is indispensable, in order to separate the mucilaginous impurities which all oil contains, and it is a precaution that should always be faithfully observed." After converting this oil into drying oil, he adds : " We always take the precaution to have five or six months' stock of this prepared oil in advance ; after which time it is better, and gives a varnish with more body and more solid drying." When, in addition to the above, it is remembered tha*-- the varnish must be kept six months, after being made, in order to allow it to ripen, it may be seen that the capital required by some firms must be very large. It is by careful attention to the above points that the English manufacturers have attained their high reputation.
This article was originally published with the title "The Manufacture of Sulphuric Acid" in Scientific American 21, 19, 293 (November 1869)