15 minutes later, two slaves bring all the things in and place them in the ground of office.

The trio take a quick view at all stuff, then turn to look at Frank.

Grant starts in a deep voice: "Here is everything you want, you gotta give us a satisfying answer."

His attitude has changed a little.

In last 15 minutes, Grant thought about the case with his brain whisked for a while. He has to admit that Frank's inference is reasonable, but there are still many confusions not revealed, for instance, the fact that all tax coins fall into the river could not be explained.

Any critical modus in it? He does not know and can't understand it.

Frank nods and crouches down in front of all the apparatus, which are candles, bamboo skewer, salt, china cups, and iron wires.

What he is going to do is actually quite simple, chemistry knowledge in high school: extract the metal, sodium, which should be impossible in ancient Rome age at all due to two difficult points: electricity and the melting point of sodium chloride.

However, Frank knows that there is a profession which is able to do it in the world.

Alchemist in R.S.T.

Alchemist is not a well-known occupation in Rome due to their notoriety during Centenary Justice, so usually they would have another identity as camouflage, physiologist, businessman, blacksmith, etc. Some zealots even believe that various inventions and devices utilized in daily life of Rome are actually from alchemists.

Honestly, Frank is not 100% sure that the explosion must be caused by sodium. But it is not important. The importance is to open up a new path to explain the explosion.

Bold assumption and rigorous reasoning are necessary prep in the early phase of the criminal investigation. The last step is to verify valid assumption and collect relevant evidence.

Frank encountered a homicide case that impressed him a lot in his last incarnation. Colleagues kept working overnight, started their brain storms according to the clues, made several speculations about the process of the case, and then collected evidence based on assumptions. Then overturned all due to their invalidity and reasoned again.

It is possible that those fake deranii is not sodium as well, but anyway, the alchemist is able to use something to replace the silver coins.

That is enough.

What he needs to do is to help these officials to move back to the right direction.

If the direction is correct, they can follow all clues to investigate, then it is not difficult to find out the mastermind behind. The case would never be solved if they still struggle in how to catch the monster; Even it has been figured out in the future, he would be banished thousands miles away from Rome City already: Sorry, you are forgotten forever.

He thaws the salt chunk with pouring water to get the brine through agitation, and covers the rice paper on the cup, then slowly pours the brine into the cup as a way to filter the brine; After the filtering, he puts the china cup over candles to roast, with the bamboo skewer stirring constantly.

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Shortly after, the brine in the cup has all been evaporated, and the crystal left is sodium chloride - Basically as we all know now - it is to purify the salt in a further pace.

Grant, Claudio, and Jessica stand aside and watch what Frank is doing.

Frank raises his head and grins at Jessica: "You are from R.S.T, right?"

He notices the compass around her waist. No one except R.S.T members know the special function of their own compass and take it everywhere.

Jessica responds with a 'yep' and smiles, "The director of R.S.T is my teacher."

The delicate and sunny oval face is a peeled egg, which is flawlessly white.

The disciple of R.S.T director .... then no need to care about her boobs ... Frank gently asks, "Could you help me to melt these crystals?"

The melting point of sodium chloride is about 800 degrees of Celsius.

Jessica shrink her small mouth: "Pyromancy is the ability of the alchemist. I'm just a geomancer."

"But my master gave me an artifact." She turns back the topic, unties the compass around her waist, fiddles with her slender fingers on the air above the compass several times, then the word "fire" lights up on the compass.

"Back off!"

Frank immediately steps back, and then, the dazzlingly bright flames are spit out, submerging the china cup.

"Stop!" Frank calls to stop soon, then inserts two iron wires into the cup promptly, and says, "Power on... oh No, should be lightning! Pay attention to voltage control ... Well, this is high maintenance, may fail multiple times."

She turns the compass, and then light up the word “lightning”; several lightning flashes in the air and touches with the iron wire.

“Zizi ....” The molten sodium chloride starts an intense chemical reaction.

"Stop!"

Frank holds his breath and leans towards the cup to check, seeing that a lump of bright silver metal is formed with some unconverted crystals and impurities on the edge.

Succeed in a single try, and the voltage has controlled very well ... Frank is pleasantly surprised. The voltage is required to 6 to 15 volts for electrolysis to produce sodium. He is ready for multiple attempts.

Unbelievably, God smiles to him, and it is done at one time.

Grant and Claudio couldn't wait to see the product closely. it is a metal chunk, which looks quite similar to silver at first glance.

Grant's pupils are shrinking with extremely shocked mind.

Claudio clenches his fists hard and looks foolishly at the metal block with the color of silver, as if lightning strikes in his mind and splits all the fog.

"Please take a look, Sir." Frank pours out the sodium into rice paper roll, wraps it over and then shake it slightly in his hand:

"It is much lighter than silver, but its appearance is very similar to silver. If someone uses it to replace silver coin, could you tell if it is silver through look? Here you go, you could feel the weight by yourself, Sir."

Then He hands over the paper roll with sodium inside to Grant. At the same time, the sodium gradually turns dim, almost the same as silver.

Claudio takes it in hand for weighing and says with shining eyes: "much lighter indeed. If this is what they escorted, then things are explicable. Miss. Mason, here you go."

Jessica takes it and then stares at Frank in a weird way: "You, are you an alchemist?"

No, I'm not, I'm just a delivery man of high school chemistry.

The bureaucrat is more active in thinking especially it is related to their performance. Grant suddenly shakes his head after temporary surprise and says grimly: "No, no, even if the denarii is replaced this way. What about the explosion? How the explosion and horrible blast happened if there are no monsters hidden in the river?"

Frank does not answer, he just takes the sodium from Jessica, walks to the desk, and throws it into the nearby fish tank.

A blazing fire light up with thick smoke billowed.

"boom!"

The sodium reacts intensely in the water, which even burst the tank with thin cracks.

"What, what the ..." Grant is stunned.

"if the denarii has been replaced by the metal, then the counterfeit coin would explode when it touches water, which can explain why the “silver coin” exploded so fiercely after falling into the river." Frank explains.

Claudio murmurs: "we were misled from the very beginning. The mastermind behind used explosion and strange wind to let us assume that it is a monster, and then focus on the monster tracking and searching."

"No wonder Aura observation spell can't detect monsters."

Frank adds: "there are some denarii gotten back from the river after all chests falling into the water. I guess they are the real silver coins spread on the top in each chest for cover."

Seamless connection among all anomalies.

"Frank Sun!" Claudio's eyes are filled with approval: "Good, you did a very good job."

Claudio looks at topless Frank, his brows suddenly wrinkles, and he just realizes that Frank does not wear any clothes in a cold day.

Then Claudio takes off his own uniform coat and puts it carefully on Frank’s body by patting his shoulder and back, and then tying all the button for him neatly.

Frank is a little surprised and grateful that the vigile genuinely shows such a high appreciation on him.

Grant frowns: "then where are the real coins since what we lost are fake?"

Jessica also gets a grim face: "Taxation are moved out from province storage and escorted into Treasury, which would be transferred through a lot of officials or their subordinates. There would be tremendous amount of them imprisoned if held accountable. Plus, the difficulty to retake the taxation is almost like to search a needle in the sea. This is something beyond our jurisdiction, we need to report to Princeps.”

Grant nods, that's what he thinks.

Claudio has a different opinion, and his voice is a little low: "Taxation was escorted all the way to Rome City, and its handover has implemented multiple times. It should be discovered long time ago if it was replaced. The only possibility is that this happens recently."

Grant's eyes light up, it greatly narrows the scope of the investigation.

"John, prepare the horse, quickly! I gotta go now!" Grant rushes out of his office eagerly.

Claudio follows instantly.

Frank does not forget to call out: "Mr. Commissioner, don't forget to release me, plus, my family members!"