APPENDIX III 558. LIST OF CHEMICAL ELEMENTS, WITH THEIR Note. SYMBOLS AND ATOMIC WEIGHTS. The words in brackets are the latin names of the elements from which the symbols have been derived. 559. THERMOMETRIC SCALES. There are two different thermometric scales in use in this country, the Centigrade and Fahrenheit; of these two the former is rapidly becoming universal for scientific purposes. The two scales are mutually convertible by the following formulæ, in which F.° represents a temperature on the Fahrenheit scale, C.° a temperature on the Centigrade scale : The temperatures occasionally referred to in this treatise are given on the Centigrade scale. WEIGHTS AND MEASURES. 560. The corresponding values of the french and english weights and measures are here given; the use of the french or decimal system is strongly recommended by its extreme simplicity, since the smaller denominations are obtained by taking a tenth, hundredth, thousandth, &c., of the unit chosen, and are designated by the latin prefixes deci-, centi-, milli-, &c., whilst the higher denominations are 10 times, 100 times, 1000, &c. times the unit, and are named by the greek prefixes deca-, hecto-, kilo-, &c. ; examples of this will be found in the tables given below. 561. The starting point of the french system is the "metre" (=39.37 inches); this is the "unit of length.' The "unit of measure" is the "litre," which is one cubic decimetre: the "unit of weight" is the gramme,* which is the weight of 1 cubic centimetre of distilled water at 4° C. The chief conveniences arising from the use of this system are:— 1st. That all the different denominations can be written as one, since they are either multiples by ten or are decimal fractions of the unit. Thus 5 decagrams, 3 grams, 4 decigrams, 8 milligrams, would be written 53.408 grams. 2nd. That since 1 cubic centimetre of water at 4° C. weighs 1 gram, we may obtain the weight of water to be used from the measure by simply converting the measure into cubic centimetres, the number thus obtained will represent at once the corresponding weight of water in grams. Of course this conversion is strictly accurate only when the water is measured at 4° C., but for ordinary purposes the error introduced when the water is at the temperature of the air is too small to be of any importance in the preparation of solutions. The weights and measures most frequently used for chemical purposes are the gram, the millimetre,t the litre, and the cubic centimetre which is of a litre. |