Intelligence and Miscellaneous Articles. 71 



decomposition of chlorate of potassium into oxygen and chloride of 

 potassium, an exothermic reaction, and not limited by its inverse, is 

 not arrested by a pressure of 320 atmospheres. In fact, from my 

 measurements, the reaction 



C10 6 K=KCl+0 6 



would liberate at the ordinary temperature +11-0. At about 400°, 

 the chlorate being fused and the chloride solid, the amount libera- 

 ted could not but be augmented. 



It is the same with the decomposition of formate by hydrate 'of 

 potass, the hydrogen continuing to be liberated even under a pres- 

 sure of more than 600 atmospheres. Here, again, is an exothermic 

 reaction not limited by its inverse. In fact the transformation of 

 the system C 2 HK0 4 +KH0 2 into C 2 6 K 2 +H 2 would liberate at the 

 ordinary temperature 



277-8-259-4= 18-4 calories. 

 At about 400°-500°, all the substances being supposed to be fused, 

 the heat disengaged would not be much modified ; for the heats of 

 fusion of the known salts but little exceed +4 calories, and the 

 initial system comprises 2 fused molecules, the final system con- 

 taining only 1. 



Thus the exothermic reactions persist, whatever may be the 

 amount of the pressure. It is nevertheless probable that the velo- 

 city of such a reaction is changed, and perhaps also the temperature 

 at which it is effected ; but the reaction itself does not cease to 

 take place. This is a fresh proof in support of the opinions 

 enunciated by the author of the present note, on a question so im- 

 portant to mechanical chemistry — opinions contested at first, but 

 which derive fresh support from every new observation*. — Annales 

 de Chimie et de Physique, October 1878, tome xv. p. 149. 



ON AN AUTOMATIC CURRENT-REGULATOR. BY M. HOSPITALIER. 



The apparatus which we have the honour to present to the Aca- 

 demy is composed of a resistance-coil wound in one layer only, the wire 

 of which has been denuded along a generatrix of the spiral over a 

 width of about 1 centimetre. A lever, somewhat convex, and f ormin g 

 a divider, is applied to the denuded part of the wire. This divider 

 is attached at one of its extremities to an armature placed before an 

 electro-magnet, in which the current circulates which is to be 

 regulated. An antagonizing spring supports the lever at its other 

 extremity. The circuit is formed by the resistance-coil, the lever, 

 and the electromagnet. The apparatus being regulated for a deter- 

 mined intensity, the divider introduces into the circuit a certain 

 number of turns of the coil. If the current increases in intensity, 

 the electromagnet attracts its armature more strongly, the divider 

 shifts its fulcrum and introduces into the circuit a greater number 



* See Chimie organique fondee sur la Synthese, t. ii. p. 349 (1860) • 

 Annales de Chimie et de Physique, 3 e ser. t. lxvi. pp. 41 & 59, t. lxviii. 

 p. 239, and especially 4 e serie, t. xviii. p. 95, and 5 e serie, t. xii. p. 310, &c. 



