VOL. LXXXV.] PHILOSOPHICAL TRANSACTIONS. 565 



their powers of producing cold with the different liquids, and the proportions of 



each, according to a careful repetition of them ; the temperature being 50°. 



Temperature, 



Salts. Liquor. or cold 



produced. 



* Sal ammoniac 5, nitre 5 water l6 + 10" 



Sal ammoniac 5, nitre 5, Glauber's salt 8 16" +4° 



* Nitrous ammoniac 1 1 + -i" 



Nitrous ammoniac 1, sal soda 1 —^ 1 — 7° 



Glauber's salt 3 d- nitr. acid 2 — o° 



Glauber's salt 6, sal ammoniac 4, nitre 2 i — 10° 



Glauber's salt 6, nitrous ammoniac 5 ■ 4 — 14° 



Phosphorated soda 9 4 — 12° 



Phosporated soda 9, nitrous ammoniac 6' 4 —21° 



Glauber's salt 8 . marine acid 5 — 0° 



Glauber's salt 5 d. vitr. acid 4 +3° 



At a higher temperature than 50°, the quantity of the salts must be increased, 

 and the effect will be proportionably greater; at a lower temperature diminished, 

 when the effect will be proportionably less. It must be observed, that to pro- 

 duce the greatest effect by any frigorific mixture, the salts should be fresh crystal- 

 lized, -|- not damp, and newly reduced to very fine powder ; the vessel in which 

 they are made very thin, and just large enough to contain the mixture ; and the 

 materials mixed intimately together, as quickly as possible, the proper proportions 

 at any temperature (those in the table being adjusted for the temperature of 50° 

 only) having been previously tried, by adding the powdered salts gradually to the 

 liquid, till the thermometer ceased to sink ; observing to produce the full effect 

 of one salt before a 2d is added, and also of the 2d before a 3d is added. Neither 

 soda, phosphorated soda, nor Glauber's salt should be mixed with nitrous am- 

 moniac, or the powder composed of sal ammoniac and nitre, unless at a low 

 temperature, i. e. below 0°, but pounded and kept apart. In the experiments 

 alluded to in the table, the precaution of fresh crystallizing the salts was not ob- 

 served, because I chose to give the ordinary effects only ; I therefore then used 

 salts in their common state, taking care however to choose such as had not in 

 the least effloresced. 



* The salts from each of these may be recovered by evaporating the mixture to dryness, and used 

 again repeatedly. The figures after each salt, and after the liquor, signify the proportion of parts, by 

 Troy weight, to be used ; the trouble of weighing the water may be saved by observing, that a full 

 ounce of it by wine measure corresponds exactly with 1 oz. of it by Troy weight ; also it must be 

 noticed, when more kinds of salt than one are used, to add them to the liquor one after the other, in 

 the order they stand in tlie table : beginning on tlie left hand, and stirring tlie mixture well between 

 each addition : d. nitr. acid, is red fuming nitrous acid 2 parts, and rain, or distilled water 1 part, 

 by weight, well agitated togetlier, and become cool : d. vitr. acid, is strong vitriolic acid, and rain, 

 or distilled water, equal parts, by weight, thoroughly mixed (very cautiously) and cooled. 



-)■ Soda, phosphorated soda, and Glaubers salt, are best crystallized afresh, because tlieir effect, 

 especially the last 2 in the acids, depend on the quantity of water they contain in a solid state. — Orig. 



