Page:The New International Encyclopædia 1st ed. v. 04.djvu/78

CALORIMETBY. 56 CALOTYPE. the 'Bunscn calorimeter' is that of Dr. Dieterici, of Hanover. (See Wiedemann's Aiinalen der Physik und der Chemie, Vol. XXXVII.. p. 494, 1889.) Fairly satisfactory descriptions are given in almost all general te.xt-books on physics. In the •steam-calorimeter" the substance whose spe- cific heat is desired is suspended on one pan of a chemical balance, which is inclosed in a box Ldnnected with a steam-boiler; if the steam is suddenly admitted, some of it will continue to condense on the pan and the substance until their temperature is raised to that of the steam. The quantity of steam thus condensed may be weighed by placing weights in the other pan of the bal- ance, and, if the latent heat of condensation of steam is known, the specific heat may easily be calculated. ' This method is due to Professor Joly. of Dublin, and a full description of the latest improvements may be foimd in the Philo- sophical Transactions of the Royal Society of London (1894). In all these methods it should be noted that what is measured is the average specific heat of the substance over a given range of temperature. For other methods of measure- ment of specific lieat, reference may be made to the larger treatises on physics. To measure the latent heat of fusion two meth- ods have been used successfully; one is an ob- vious application of the method of mixtures; the other is to secure the fusion by means of the heating action of an electric current, whose in- tensity and electromotive force may be measured, thus giving the quantity of energy consumed in producing the fusion. To measure the latent heat of evaporation, two similar methods have been used, and a third also. If the vapor is conducted through a long spiral tube surrounded by water, the vapor will con- dense, the temperature of the water will be raised, and thus we have simply the method of mixtures. Or a liquid may be made to evaporate by means of a reduced pressure, and the conse- quent fall of temperature may be balanced by the heating action of a known electric current. Again, if a liquid inclosed in a Bunsen calorim- eter is caused to evaporate, the surrounding water will be frozen — just the reverse of the gen- eral use of the apparatus— and the quantity frozen may be measured. For full description of these various methods for measuring latent heats of all kinds, reference should be made to general treatises on heat, Preston, Theory of Heat (Lon- don, 1894), is perhaps the best book of reference. Another class of calorimeters is designed to enable the observ'er to ascertain the number of calories furnished when certain fuels, such as coals, oils, etc., are allowed to burn under definite conditions. In these the coal is placed in a hol- low steel cylinder which can be tightly closed, oxygen is admitted under high pressure, and com- bustion is started by means of an electric cur- rent through a fuse wire. The cylinder is kept immersed in wa'ter, the rise of temperature of which is obser'ed. and the energy' generated thus measured. Calorimeters constructed on a large scale are used to measure the amount of heat given ofT by an animal or human being, the amount of food and air supplied to the subject of the test being recorded. Prof, W, O. Atwater, of Wesleyan University, has carried on a num- ber of experiments with such an instrument, and has ascertained the fuel value of various foods. Hia results are to be found in a series of bulle- tins issued by the United States Department of Agriculture. CALOTTISTES, ka'16'tfst' (Fr. Calottiste, from calotte, dimin. of OF. cale, cap.) A society of wits and satirists in the time of Louis XIV. and Louis XV., known as the Regiment de la Calotte. They were headed by two officers in the King's Ijodygxiard, named Torsac and Aymond. Their amusement consisted in sending to any pub- lic character who had exposed himself to ridicule a 'patent' authorizing him to wear the calotte as a covering for the weak part of his head. The armo- rial bearings of the Regiment de la Calotte con- sisted of various symbols of folly, with the mottoes C'est rcgner que de sacoir rire, and Fa vet ilomiis, Luna Influit. When Torsac, its first 'generalissi- mo,' died, the society, which occupied a position of satirical hostility to the French Academy, drew up a burlesque funeral oration, manufactured out of the pompously eulogistic phrases which the academicians were in the habit of using. As the society became more audacious and did not spare even royalty itself, it was dissolved by the Jlin- ister, Fleurv. The Mcmoircs pour scrvir a I'his- toire de la Calotte (Basel, 1725) is an amusing little book. During the Bourbon Restoration the title Regime de la Calotte was applied to the priestly administration of affairs. CAL'OTYPE (Gk. koXAs, kulos, beautiful, + T&iroi, typos, impression). A name applied to one of the earliest processes for producing photo- graphic prints, as well as to the prints them- selves. The process was invented by Henry Fox Talbot in 1840. It consists of the following oper- ations. A sheet of good plain paper with a smooth surface and a close and even texture, is washed by means of a soft brush with a solu- tion of 100 grains of crystallized silver nitrate in 6 ounces of distilled water. Tlie paper is allowed to dry in a dark room and is then dipped into a solution of potassium iodide made by dis- solving 500 grains of that salt in a pint of water. After a few minutes it is removed and then dipped into water and dried. This 'iodized paper' is exceedingl.y sensitive to light, and may be kept for some time if it is carefully protected from sunlight. When required for use. a sheet of it is washed in a mixture which Jlr, Talbot called gallo-nitrate of silver. The mixture is obtained by adding a saturated solution of gallic acid to an equal volume of a solution of 100 grains of crystallized silver nitrate in 2 ounces of distilled water, to which one-sixth of its volume of strong acetic acid had been added. After the iodized paper has been washed over with this solution it is dipped into water and then cautiously dried with blotting-paper. An exposure of less than a second in diffused daylight is sufficient to obtain an impression. In order to develop the impres- sion the paper is again washed with gallo-nitrate of silver and dried near a fire, the exposed por- tions becoming brown, while the covered portions retain their original color. The picture is then fi.xed by consecutively washing it in clean water, drying, washing in a solution of potassium bro- mide (100 grains in 8 ounces of water), washing in water to remove any surplus iodide solution, and finally drying. The calotype process has been superseded by other processes, and is at present hardly ever used. See Photography.