758 TRAXSACTrONS OF THE AMERICAN INSTITUTE. 



whicli embody tlie principal conclusions to wliicli an examination of 

 tlie cited cases of gradual chemical change has led : 1. Tlie rate at 

 which, a chemical change proceeds is constant under constant con- 

 ditions, and is independent of the time that lias elapsed since the 

 change commenced. 2. When any substance is undergoing a chemical 

 change, of which no condition varies, excepting the diminiition of the 

 changing substance, the amount of change occurring at any moment 

 is directly proportional to the quantity of the substance. 3. When 

 two or more substances act one upon another, the amount of action 

 at any moment is directly proportioned to the quantity of each of the 

 substances, tt. When the rate of any chemical change is affected by 

 the presence of a substance, which itself takes no part in the change, 

 the acceleration or retardation produced is directly proportional to 

 the quantity of the substance. 5. The relation between the rate 

 of a chemical change occurring in a solution, and the temperature of 

 the solution is such that for every additional degree the number 

 expressing the rate is to be multiplied by a constant quantity. 



Ckystallization' of Sulwiue. 

 M. Schutzenbei'ger has proved, by experiment, that pure melted 

 sulphur may be crystallized, a little below 212 degrees Fahr., in octa- 

 hedra of the fourth system, without the aid of any solvent. 



Xew Device for Manufactuking Suli'iiueic Acid. 



The apparatus, invented by Mr. Lardani, consists of a furnace for 

 burning sulphur and forming sulphurous acid, a washer or scrubber, 

 a refrigerator, a reacting vessel, and a regenerator for nitric acid. 

 The warm sulphurous acid gas, made by l)urning sulphur and forced 

 out of the furnace by a current of air, which furnishes oxygen, enters 

 the scru])l)er and is freed from volatilized sulphur, and especially arse- 

 nious acid when arsenical pyrites is used, as tlie source of sulphur. 

 After passing through the refrigerator it enters the reacting vessel, 

 composed of two parts, the lower containing nitric acid, and the upper 

 pumice stone, resting on plates of lead or aluminum, pierced witli 

 holes. The gas passes through the nitric acid, and after receiving 

 ■ another equivalent of oxygen it sinks, in the form of snlphuric acid, 

 to the bottom, while the hyponitric escapes throngli the pumice stone, 

 and, traversing the upper part of tlic apparatus, enters the regenera- 

 tor, where, meeting with an excess of nitrogen, it is transformed into 

 nitric acid, and ready to be used again in oxidizing sulphurous acid. 



